11 results on '"Marsaleix, P."'
Search Results
2. New insights into the South China Sea throughflow and water budget seasonal cycle: evaluation and analysis of a high-resolution configuration of the ocean model SYMPHONIE version 2.4
- Author
-
N. B. Trinh, M. Herrmann, C. Ulses, P. Marsaleix, T. Duhaut, T. To Duy, C. Estournel, and R. K. Shearman
- Subjects
Geology ,QE1-996.5 - Abstract
The South China Sea throughflow (SCSTF) connects the South China Sea (SCS) with neighboring seas and oceans, transferring surface water of the global thermohaline circulation between the Pacific and Indian oceans. A configuration of the SYMPHONIE ocean model at high resolution (4 km) and including an explicit representation of tides is implemented over this region, and a simulation is analyzed over 2010–2018. Comparisons with in situ and satellite data and other available simulations at coarser resolution show the good performance of the model and the relevance of the high resolution for reproducing the spatial and temporal variability of the characteristics of surface dynamics and water masses over the SCS. The added value of an online computation of each term of the water, heat, and salt SCS budgets (surface, lateral oceanic and river fluxes, and internal variations) is also quantitatively demonstrated: important discards are obtained with offline computation, with relative biases of ∼40 % for lateral oceanic inflows and outflows. The SCS water volume budget, including the SCSTF, is analyzed at climatological and seasonal scales. The SCS receives on average a 4.5 Sv yearly water volume input, mainly from the Luzon Strait. It laterally releases this water to neighboring seas, mainly to the Sulu Sea through Mindoro Strait (49 %), to the East China Sea via Taiwan Strait (28 %), and to the Java Sea through Karimata Strait (22 %). The seasonal variability of this water volume budget is driven by lateral interocean exchanges. Surface interocean exchanges, especially at Luzon Strait, are all driven by monsoon winds that favor winter southwestward flows and summer northeastward surface flows. Exchanges through Luzon Strait deep layers show a stable sandwiched structure with vertically alternating inflows and outflows. Last, differences in flux estimates induced by the use of a high-resolution model vs. a low-resolution model are quantified.
- Published
- 2024
- Full Text
- View/download PDF
3. Seasonal dynamics and annual budget of dissolved inorganic carbon in the northwestern Mediterranean deep-convection region
- Author
-
C. Ulses, C. Estournel, P. Marsaleix, K. Soetaert, M. Fourrier, L. Coppola, D. Lefèvre, F. Touratier, C. Goyet, V. Guglielmi, F. Kessouri, P. Testor, and X. Durrieu de Madron
- Subjects
Ecology ,QH540-549.5 ,Life ,QH501-531 ,Geology ,QE1-996.5 - Abstract
Deep convection plays a key role in the circulation, thermodynamics, and biogeochemical cycles in the Mediterranean Sea, which is considered to be a hotspot of biodiversity and climate change. In the framework of the DEWEX (Dense Water Experiment) project, the seasonal and annual budgets of dissolved inorganic carbon in the deep-convection area of the northwestern Mediterranean Sea are investigated over the period September 2012–September 2013 using a 3D coupled physical–biogeochemical–chemical modeling approach. At the annual scale, we estimate that the northwestern Mediterranean Sea's deep-convection region was a moderate sink of 0.5 mol C m−2 yr−1 of CO2 for the atmosphere. The model results show the reduction of oceanic CO2 uptake during deep convection and its increase during the abrupt spring phytoplankton bloom following the deep-convection events. We highlight the major roles in the annual dissolved inorganic carbon budget of both the biogeochemical and physical fluxes, which amount to −3.7 and 3.3 mol C m−2 yr−1, respectively, and are 1 order of magnitude higher than the air–sea CO2 flux. The upper layer (from the surface to 150 m depth) of the northwestern deep-convection region gained dissolved inorganic carbon through vertical physical transport and, to a lesser extent, oceanic CO2 uptake, and it lost dissolved inorganic carbon through lateral transport and biogeochemical fluxes. The region, covering 2.5 % of the Mediterranean, acted as a source of dissolved inorganic carbon for the surface and intermediate water masses of the Balearic Sea and southwestern Mediterranean Sea and could represent up to 22 % and 11 %, respectively, of the CO2 exchanges with the Atlantic Ocean at the Strait of Gibraltar.
- Published
- 2023
- Full Text
- View/download PDF
4. Seasonal and interannual variability of the pelagic ecosystem and of the organic carbon budget in the Rhodes Gyre (eastern Mediterranean): influence of winter mixing
- Author
-
J. Habib, C. Ulses, C. Estournel, M. Fakhri, P. Marsaleix, M. Pujo-Pay, M. Fourrier, L. Coppola, A. Mignot, L. Mortier, and P. Conan
- Subjects
Ecology ,QH540-549.5 ,Life ,QH501-531 ,Geology ,QE1-996.5 - Abstract
The Rhodes Gyre is a cyclonic persistent feature of the general circulation of the Levantine Basin in the eastern Mediterranean Sea. Although it is located in the most oligotrophic basin of the Mediterranean Sea, it is a relatively high primary production area due to strong winter nutrient supply associated with the formation of Levantine Intermediate Water. In this study, a 3D coupled hydrodynamic–biogeochemical model (SYMPHONIE/Eco3M-S) was used to characterize the seasonal and interannual variability of the Rhodes Gyre's ecosystem and to estimate an annual organic carbon budget over the 2013–2020 period. Comparisons of model outputs with satellite data and compiled in situ data from cruises and Biogeochemical-Argo floats revealed the ability of the model to reconstruct the main seasonal and spatial biogeochemical dynamics of the Levantine Basin. The model results indicated that during the winter mixing period, phytoplankton first progressively grow sustained by nutrient supply. Then, short episodes of convection driven by heat loss and wind events, favoring nutrient injections, organic carbon export, and inducing light limitation on primary production, alternate with short episodes of phytoplankton growth. The estimate of the annual organic carbon budget indicated that the Rhodes Gyre is an autotrophic area, with a positive net community production in the upper layer (0–150 m) amounting to 31.2 ± 6.9 gCm-2yr-1. Net community production in the upper layer is almost balanced over the 7-year period by physical transfers, (1) via downward export (16.8 ± 6.2 gCm-2yr-1) and (2) through lateral transport towards the surrounding regions (14.1 ± 2.1 gCm-2yr-1). The intermediate layer (150–400 m) also appears to be a source of organic carbon for the surrounding Levantine Sea (7.5 ± 2.8 gCm-2yr-1) mostly through the subduction of Levantine Intermediate Water following winter mixing. The Rhodes Gyre shows high interannual variability with enhanced primary production, net community production, and exports during years marked by intense heat losses and deep mixed layers. However, annual primary production appears to be only partially driven by winter vertical mixing. Based on our results, we can speculate that future increase of temperature and stratification could strongly impact the carbon fluxes in this region.
- Published
- 2023
- Full Text
- View/download PDF
5. On the role of wind and tides in shaping the Gironde River plume (Bay of Biscay)
- Author
-
Toublanc, F., Ayoub, N.K., and Marsaleix, P.
- Published
- 2023
- Full Text
- View/download PDF
6. The role of wind, mesoscale dynamics, and coastal circulation in the interannual variability of the South Vietnam Upwelling, South China Sea – answers from a high-resolution ocean model
- Author
-
T. To Duy, M. Herrmann, C. Estournel, P. Marsaleix, T. Duhaut, L. Bui Hong, and N. Trinh Bich
- Subjects
Geography. Anthropology. Recreation ,Environmental sciences ,GE1-350 - Abstract
The South Vietnam Upwelling (SVU) develops in the South China Sea (SCS) under the influence of southwest monsoon winds. To study the role of small spatiotemporal scales on the SVU functioning and variability, a simulation was performed over 2009–2018 with a high-resolution configuration (1 km at the coast) of the SYMPHONIE model implemented over the western region of the SCS. Its capability to represent ocean dynamics and water masses from daily to interannual scales and from coastal to regional areas is quantitatively demonstrated by comparison with available satellite data and four in situ datasets. The SVU interannual variability is examined for the three development areas already known: the southern (SCU) and northern (NCU) coastal upwelling areas and the offshore upwelling area (OFU). Our high-resolution model, together with in situ observations and high-resolution satellite data, moreover shows for the first time that upwelling develops over the Sunda Shelf off the Mekong Delta (MKU). Our results confirm for the SCU and OFU and show for the MKU the role of the mean summer intensity of wind and cyclonic circulation over the offshore area in driving the interannual variability of the upwelling intensity. They further reveal that other factors contribute to SCU and OFU variability. First, the intraseasonal wind chronology strengthens (in the case of regular wind peaks occurring throughout the summer for SCU or of stronger winds in July–August for OFU) or weakens (in the case of intermittent wind peaks for SCU) the summer average upwelling intensity. Second, the mesoscale circulation influences this intensity (multiple dipole eddies and associated eastward jets developing along the coast enhance the SCU intensity). The NCU interannual variability is less driven by the regional-scale wind (with weaker monsoon favoring stronger NCU) and more by the mesoscale circulation in the NCU area: the NCU is prevented (favored) when alongshore (offshore) currents prevail.
- Published
- 2022
- Full Text
- View/download PDF
7. Particulate organic carbon dynamics in the Gulf of Lion shelf (NW Mediterranean) using a coupled hydrodynamic–biogeochemical model
- Author
-
G. Many, C. Ulses, C. Estournel, and P. Marsaleix
- Subjects
Ecology ,QH540-549.5 ,Life ,QH501-531 ,Geology ,QE1-996.5 - Abstract
The Gulf of Lion shelf (GoL, NW Mediterranean) is one of the most productive areas in the Mediterranean Sea. A 3D coupled hydrodynamic–biogeochemical model is used to study the mechanisms that drive the particulate organic carbon (POC) dynamics over the shelf. A set of observations, including temporal series from a coastal station, remote sensing of surface chlorophyll a, and a glider deployment, is used to validate the distribution of physical and biogeochemical variables from the model. The model reproduces the time and spatial evolution of temperature, chlorophyll a, and nitrate concentrations well and shows a clear annual cycle of gross primary production and respiration. We estimate an annual net primary production of ∼ 200 × 104 t C yr−1 at the scale of the shelf. The primary production is marked by a coast-slope increase with maximal values in the eastern region. Our results show that the primary production is favoured by the inputs of nutrients imported from offshore waters, representing 3 and 15 times the inputs of the Rhône in terms of nitrate and phosphate. In addition, the empirical orthogonal function (EOF) decomposition highlights the role of solar radiation anomalies and continental winds that favour upwellings, and inputs of the Rhône River, in annual changes in the net primary production. Annual POC deposition (27 × 104 t C yr−1) represents 13 % of the net primary production. The delivery of terrestrial POC favours the deposition in front of the Rhône mouth, and the mean cyclonic circulation increases the deposition between 30 and 50 m depth from the Rhône prodelta to the west. Mechanisms responsible for POC export (24 × 104 t C yr−1) to the open sea are discussed. The export off the shelf in the western part, from the Cap de Creus to the Lacaze-Duthiers canyon, represents 37 % of the total POC export. Maximum values are obtained during shelf dense water cascading events and marine winds. Considering surface waters only, the POC is mainly exported in the eastern part of the shelf through shelf waters and Rhône inputs, which spread to the Northern Current during favourable continental wind conditions. The GoL shelf appears as an autotrophic ecosystem with a positive net ecosystem production and as a source of POC for the adjacent NW Mediterranean basin. The undergoing and future increase in temperature and stratification induced by climate change could impact the trophic status of the GoL shelf and the carbon export towards the deep basin. It is crucial to develop models to predict and assess these future evolutions.
- Published
- 2021
- Full Text
- View/download PDF
8. Variability of the Red River Plume in the Gulf of Tonkin as Revealed by Numerical Modeling and Clustering Analysis
- Author
-
Tung Nguyen-Duy, Nadia K. Ayoub, Patrick Marsaleix, Florence Toublanc, Pierre De Mey-Frémaux, Violaine Piton, Marine Herrmann, Thomas Duhaut, Manh Cuong Tran, and Thanh Ngo-Duc
- Subjects
Red River ,river plume ,coastal ocean modeling ,K-means ,clustering analysis ,passive tracers ,Science ,General. Including nature conservation, geographical distribution ,QH1-199.5 - Abstract
We study the daily to interannual variability of the Red River plume in the Gulf of Tonkin from numerical simulations at high resolution over 6 years (2011–2016). Compared with observational data, the model results show good performance. To identify the plume, passive tracers are used in order to (1) help distinguish the freshwater coming from different continental sources, including the Red River branches, and (2) avoid the low salinity effect due to precipitation. We first consider the buoyant plume formed by the Red River waters and three other nearby rivers along the Vietnamese coast. We show that the temporal evolution of the surface coverage of the plume is correlated with the runoff (within a lag), but that the runoff only cannot explain the variability of the river plume; other processes, such as winds and tides, are involved. Using a K-means unsupervised machine learning algorithm, the main patterns of the plume and their evolution in time are analyzed and linked to different environmental conditions. In winter, the plume is narrow and sticks along the coast most of the time due to the downcoast current and northeasterly wind. In early summer, the southwesterly monsoon wind makes the plume flow offshore. The plume reaches its highest coverage in September after the peak of runoff. Vertically, the plume thickness also shows seasonal variations. In winter, the plume is narrow and mixed over the whole water depth, while in summer, the plume can be detached both from the bottom and the coast. The plume can deepen offshore in summer, due to strong wind (in May, June) or specifically to a recurrent eddy occurring near 19°N (in August). This first analysis of the variability of the Red River plume can be used to provide a general picture of the transport of materials from the river to the ocean, for example in case of anthropogenic chemical substances leaked to the river. For this purpose, we provide maps of the receiving basins for the different river systems in the Gulf of Tonkin.
- Published
- 2021
- Full Text
- View/download PDF
9. High resolution modeling of the Indian Ocean circulation designed for Lagrangian dispersion applied to marine plastic pollution
- Author
-
Weiss, L., Herrmann, M., Maes, C., Marsaleix, P., Bompoil, M., and Duhaut, T.
- Abstract
Our project is part of an international and multidisciplinary IRD collaboration aiming to better understand the distribution of plastic litter in the Indian Ocean. This basin, rich in biodiversity, is subject to strong anthropogenic pressure with more than 2.2 billion inhabitants connected to the Ocean via river basins and intense maritime traffic (Honorato-Zimmer et al., 2022). The ocean dynamics is complex, with strong regional and seasonal variability and intense eddy activity as in the Mozambique Channel. To address these issues, we have developed a configuration of the hydrodynamic model SYMPHONIE (Marsaleix et al., 2008) over the Indian Ocean to study the land-sea transfers and sub-basins connectivity. We created a curvilinear grid with two high resolution poles, of the order of 1km, centered on the Mozambique Channel and the Indian coast, from the Arabian Sea to the Bay of Bengal. We show that this high resolution allows us to represent the mesoscale and partly sub-mesoscale structures that play a fundamental role in the transfer and retention of particles at sea. Our simulation is forced by daily riverine freshwater discharges whose plumes influence coastal and seasonal dynamics but also plastic river inputs (Weiss et al., 2021). Thus, we address the challenges of locating and quantifying anthropogenic sources in modeled plastic deployment scenarios as well as simulating their dispersion affected by sinking or rising velocities in ocean currents. Finally, we propose to assess the potential impact by characterizing the major beaching areas co-located with mangrove, coral and sandy coastlines distributed around the basin., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)
- Published
- 2023
- Full Text
- View/download PDF
10. The influence of freshwater input on the dynamics of the Indonesian Seas
- Author
-
Pratama, B., Maes, C., Ramdhani, A., Herrmann, M., and Marsaleix, P.
- Abstract
This study aimed to examine the effect of freshwater river discharge on dynamics of the Indonesian Seas using the high-resolution (5 km) SYMPHONIE model. Two simulations were performed considering the river-runoff-input(RRI) and non-river-runoff-input(NRI) during the 2009-2019 period. Daily GloFAS data was utilized as the river flow input and validated against actual river discharge data in Indonesia, showing maximum correlation values of 0.86 in Kalimantan. The validity of the sea surface salinity (SSS) simulated by the model was assessed by comparison with data obtained from the SMOS, SMAP, and CCI satellite products. The results indicated that the RRI simulation better agrees with the observational data, with a highly significant linear correlation coefficient of 0.95. A detailed analysis of RRI simulation and observational data revealed good agreement between the observed and simulated patterns of low SSS and high variability in several river mouths located off the Java Sea, such as the Barito River in Kalimantan, Musi and Sindang rivers in Sumatera. SSS values in the Western-Java-Sea (WJV) and Eastern-Java-Sea (EJV) revealed consistent seasonal variations, with minima observed in DJF and MAM seasons and maxima during SON season in both areas.In terms of ocean dynamics,RRI in WJV revealed shallower Mixed-Layer-Depth and Isothermal-Layer-Depth by 5–10 meters throughout the seasons while in the EJV, significant changes were revealed during the SON and thicker Barrier-Layer-Thickness in both areas during DJF and MAM seasons as compared to NRI. Further analysis of the various mechanisms and factors impacting ITFs will also be presented and discussed., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)
- Published
- 2023
- Full Text
- View/download PDF
11. Internal Tides Responsible for Lithogenic Inputs Along the Iberian Continental Slope
- Author
-
Barbot, Simon, Lagarde, Marion, Lyard, Florent, Marsaleix, Patrick, Lherminier, Pascale, and Jeandel, Catherine
- Abstract
This study proposes new insights for the interpretation of GEOVIDE particle measurements. Potential resuspension sites due to internal tides (ITs) have been identified along the western Iberian shelf slope using a tidal regional model. Iberian shelf is mainly a source of lithogenic material whereas Galicia Bank is a source of biogenic matter. The potential pathways for particles from the resuspension sites toward the GEOVIDE stations are identified using IBIRYS reanalysis to infer their transport by the ocean circulation. It appears that each station is influenced by a specific pathway and mixed particles from several resuspension sites. This methodology reveals that the criticality of the bathymetry slope, commonly used to track resuspension sites from internal waves, is not sufficient to investigate ITs. An explicit resolution of ITs using a numerical tidal model is required for an exhaustive identification of the resuspension sites. Internal tides (ITs) are waves with a tidal period generated when tides cross a steep slope of the sea floor. ITs then propagate in every stratified layer of the open ocean over hundreds to thousands of kilometers. The encounter of ITs with underwater relief, either at the generation site or after propagation, results in high bottom friction that enhances sediment resuspension. Evidence of lithogenic particles was found at various depths during the GEOVIDE cruise, from the Iberian continental slope to thousands of kilometers away. The present study identifies the sites where ITs are responsible for sediment resuspension. Additionally, the oceanic circulation is investigated to establish the trajectories of the resuspended sediment that could explain the GEOVIDE measurements. Sites of high bottom tidal velocity along the Iberian continental slope were identified using a semi‐realistic internal tides modelSediment resuspension was confirmed on five sites based on earlier sediment surveys and Shields criterion thresholdParticle trajectories were proposed based on circulation modeling to improve the interpretation of geochemical tracers measurements Sites of high bottom tidal velocity along the Iberian continental slope were identified using a semi‐realistic internal tides model Sediment resuspension was confirmed on five sites based on earlier sediment surveys and Shields criterion threshold Particle trajectories were proposed based on circulation modeling to improve the interpretation of geochemical tracers measurements
- Published
- 2022
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.