Search

Your search keyword '"Dadou I."' showing total 86 results
Start Over Author "Dadou I."
86 results on '"Dadou I."'

2. Influence of the Gulf of Guinea islands on the Atlantic Equatorial Undercurrent circulation

Author

Napolitano, D. C., Alory, G., Dadou, I., Morel, Y., Jouanno, J., Morvan, G., Napolitano, D. C., Alory, G., Dadou, I., Morel, Y., Jouanno, J., and Morvan, G.

Abstract

In the easternmost portion of the Gulf of Guinea, Bioko Island marks the beginning of an island chain that stretches NE–SW to the Equator, where São Tomé Island sits in the path of the Equatorial Undercurrent (EUC). In this study, we explore the meso-to-large-scale effects of local flow-topography interactions that escalate from the EUC encounter with the Gulf of Guinea islands. A mean shipboard ADCP section captures the EUC as a strong subsurface jet that ultimately hits São Tomé. Motivated by these observations, we ran two ocean general circulation model simulations that differ by the presence versus absence of the Gulf of Guinea islands. Diagnostics of salinity and potential vorticity (PV) from these simulations show that the EUC bifurcates at 6°E, triggering mesoscale activity that spreads the EUC waters. On both sides of São Tomé, the EUC branches roll up into eddies that propagate westward. These low-PV anticyclones carry high salinity through the tropical Atlantic, introducing PV anomalies along eddy corridors mirrored by the Equator. The formation of such eddies is affected by diapycnal and isopycnal mixing and friction, and their distribution between hemispheres is intrinsically related to the location of São Tomé. The eddies are modulated at both seasonal and interannual scales. A strong EUC generates numerous and stronger eddies, while seasonal equatorial upwelling indirectly hinders their formation. Convergence of the EUC upstream of São Tomé reveals intense downwelling and freshening, whereas divergence and upwelling are associated with the EUC negotiating the island. Key Points Velocity observations show that the EUC hits São Tomé Island at 6°E, forcing the jet to bifurcate earlier than if the island did not exist The EUC dynamics and the location of São Tomé impose an asymmetry to the bifurcation, affecting net zonal fluxes in the tropical Atlantic The EUC-island encounter triggers vertical advection and transformation of the EUC water via diapycnal a

Published
2022
Full Text
View/download PDF

3. TRISHNA: An Indo-French Space Mission to Study the Thermography of the Earth at Fine Spatio-Temporal Resolution

Author

Roujean, J.-L., primary, Bhattacharya, B., additional, Gamet, P., additional, Pandya, M. R., additional, Boulet, G., additional, Olioso, A., additional, Singh, S. K., additional, Shukla, M. V., additional, Mishra, M., additional, Babu, S., additional, Raju, P. V., additional, Murthy, C. S., additional, Briottet, X., additional, Rodler, A., additional, Autret, E., additional, Dadou, I., additional, Adlakha, D., additional, Sarkar, M., additional, Picard, G., additional, Kouraev, A., additional, Ferrari, C., additional, Irvine, M., additional, Delogu, E., additional, Vidal, T., additional, Hagolle, O., additional, Maisongrande, P., additional, Sekhar, M., additional, and Mallick, K., additional

Published
2021
Full Text
View/download PDF

5. Impact of Internal Tides on Distributions and Variability of Chlorophyll‐a and Nutrients in the Indonesian Seas

Author

Capuano, T. A., Koch‐Larrouy, A., Nugroho, D., Zaron, E., Dadou, I., Tran, K., Vantrepotte, V., and Allain, D.

Abstract

Internal tides (ITs) in the Indonesian Seas were largely investigated and held responsible for strong water mass transformation and intense surface cooling. Here, we evaluate the ITs' impact on chlorophyll‐a through a coupled INDESO ocean‐biogeochemical model which is compared with in situ data and satellite products. The results show that explicit tides' inclusion within the model improves the representation of chlorophyll‐a and nutrients. Previous studies highlighted that tides at spring‐neap cycle cool the surface water by 0.2°C. Our current results show increases of chlorophyll‐a by 0.2 up to 5 × 10−7mg Chl m−3(in log10) at ITs' generation sites (Sangihe, Ombai, Banda, and Halmahera Straits) and over the shallow Australian plateau and Java Sea, where barotropic tidal friction is high (Zaron et al., 2023, https://doi.org/10.5194/os‐19‐43‐2023). In addition, maxima of chlorophyll‐a concentration have a spring‐neap tides pulse in good agreement with ocean color images. We use INDOMIX in situ vertical diffusivities in a 1D diffusion model to explain the biogeochemical tracers' transformation within the Halmahera Sea and to estimate the nutrients' turbulent flux. We find an associated increase in new production of ∼25% of the total and an increase in mean chlorophyll‐a of ∼30%. These findings support the idea of enhanced surface mixing capable of providing cold and nutrient‐rich water favorable for the phytoplankton growth. Hence, we confirm the key role of ITs in shaping vertical distribution and variability of chlorophyll‐a, along with nutrients and oxygen, in the Indonesian archipelago at the hotspots of intensified mixing where strong ITs are found. Internal tides in the Indonesian Seas have been largely studied in the last two decades and hotspots of vertical mixing have been identified in the straits along the Indonesian Throughflow. Previous model findings and satellite observations show that this mixing causes a cooling effect on the sea surface temperature amplified by the spring‐neap cycle. The effects of tidal mixing on chlorophyll‐a has been always hypothesized but never investigated. The aim of our study is to quantify the impact of internal tides on chlorophyll‐a distribution through the analysis of coupled physical and biogeochemical numerical simulations. Comparisons to both in situ observations and ocean‐color satellite data are used to validate the model and demonstrate that mixing due to tides is a key process for the vertical distribution and variability of chlorophyll‐a, as well as nutrients and oxygen, in the Indonesian Seas. Internal tides mixing plays a key role in structuring physical and biogeochemical properties within the Indonesian SeasTidal forcing induces chlorophyll‐a fluctuations at the MSf frequency(M2‐S2, 14.8 days, spring/neap tides) with important implicationsTurbulent flux of nutrients driven by internal tides in the euphotic layer leads to an increase in mean chlorophyll‐a concentration Internal tides mixing plays a key role in structuring physical and biogeochemical properties within the Indonesian Seas Tidal forcing induces chlorophyll‐a fluctuations at the MSf frequency(M2‐S2, 14.8 days, spring/neap tides) with important implications Turbulent flux of nutrients driven by internal tides in the euphotic layer leads to an increase in mean chlorophyll‐a concentration

Published
2025
Full Text
View/download PDF

6. TRISHNA: a high spatio-temporal resolution Indian-French spatial mission for TIR Earth observation

Author

Lagouarde, Jean-Pierre, Bhattacharya, B., Crebassol, P., Gamet, P., Murthy, C., Babu, S., Boulet, G., Briottet, X., Adlakha, D., Dadou, I., Dedieu, G., Gouhier, M., Hagolle, O., Irvine, Mark, Jacob, Frédéric, Kumar, K., Laignel, Benoît, Maisongrande, P., Mallick, K., Ottlé, C, Olioso, Albert, Pandya, M., Raju, P., Roujean, J.L., Shukla, M., Singh, S., Mishra, M., Nigam, R., A. Sobrino, J., Ramakrishnan, R., Interactions Sol Plante Atmosphère (UMR ISPA), Institut National de la Recherche Agronomique (INRA)-Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine (Bordeaux Sciences Agro), Centre National d'Études Spatiales [Toulouse] (CNES), Centre d'études spatiales de la biosphère (CESBIO), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), ONERA / DOTA, Université de Toulouse [Toulouse], ONERA-PRES Université de Toulouse, Laboratoire d'étude des Interactions Sol - Agrosystème - Hydrosystème (UMR LISAH), Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Morphodynamique Continentale et Côtière (M2C), Université de Caen Normandie (UNICAEN), Normandie Université (NU)-Normandie Université (NU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rouen Normandie (UNIROUEN), Normandie Université (NU)-Centre National de la Recherche Scientifique (CNRS), Luxembourg Institute of Science and Technology (LIST), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes (EMMAH), Avignon Université (AU)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Facultat de Fisica [València] (UV), and Universitat de València (UV)

Subjects
remote sensing, water stress, cycle de l'eau, water management, télédétection, satellite, [SDE]Environmental Sciences, évapotranspiration, hydrology, Thermal infrared, TRISHNA, coastal water
Abstract

The climate change context, along with the increasing scarcity and deteriorating quality of the water resource leads to monitor different components of the water cycle. A particular attention has to be paid to some areas, particularly, agricultural lands which represent about 70% of the water consumption, and coastal areas subject to strong interactions with land. Thermal infrared (TIR) data from space are well adapted to these purposes, but the spatial variability of the surface requires that the complexity of both physical and biological processes involved must be assessed at a smaller scale which corresponds to the scale at which decisions concerning water management or implementation of policies devoted to the mitigation of climate change effect are effective. In addition, surface fluxes show short-time scale variability, which requires frequent observations to be done. The need of space borne systems combining both high spatial resolution and high revisit frequency in thermal infrared (TIR), which do not exist today, is now largely recognized by the scientific community and end-users, especially as SENTINEL and RESOURCESAT missions now provide high quality complementary data in the optical domain. To fill this gap a project, TRISHNA (Thermal infraRed Imaging Satellite for High-resolution Natural resource Assessment), is currently in the feasibility assessment phase, conducted by the French Space Agency (CNES) and the Indian Space Research Organization (ISRO).Two scientific objectives drive the mission specifications, (i) monitoring of ecosystem stress of the continental biosphere and of water use with applications to agriculture and hydrology, and (ii) monitoring of coastal and continental waters. Four complementary goals enlarge the community aggregated around the project: (iii) urban microclimates monitoring (urban heat islands, mitigation of heat waves effects…), (iv) applications to Solid Earth/geology (detection of thermal anomalies, volcanology, peat fires…), (v) cryosphere monitoring (glaciers, polar regions…), and (vi) applications to atmosphere (water content, clouds…). These objectives and the expected applications will first be briefly reviewed at the symposium.The main mission specifications will then be presented. Additionally to previous work conducted to consolidate the revisit and resolution specifications, emphasis will be put on recent studies made for inventorying factors possibly perturbing surface temperature measurements. Significant advances obtained for characterizing and modelling TIR directional anisotropy and thermal hot spot effects will first be described and their impact on the choice of orbit discussed. Similarly, an original study of the impact of atmospheric turbulence on the accuracy of LST -largely ignored by the community till date- will be presented; it reinforces the need of high revisit, and allows to estimate the errors on LST measurements. An overpass time in the early afternoon, around 13:00 LST has been carefully justified to cope with the different objectives of the mission and to optimize the accuracy on retrieved fluxes. A baseline spectral configuration of 4 TIR channels within the range 8 - 12 µm is under study, which makes possible implementing both split-window and temperature-emissivity separation algorithms. The main specifications of VNIR instrument embarked aboard the same platform are presented, and the need of 6 bands, 4 in the VNIR (blue, green, red, near infrared at 485, 555, 670, 860 nm) and 2 in the SWIR (1.38 and 1.61 µm) justified. To cope with the requirement of global coverage at Equator with a single satellite, a revisit of 3 days is selected. The nadir resolution of 50 m is binned at 1 km over open ocean. The instrumental studies undertaken will be briefly presented.The programmatic context of existing missions will be analyzed, only TRISHNA and the ESA LSTM mission providing high spatio-temporal capacities. The forthcoming phases of the CNES-ISRO TRISHNA project will finally be briefly mentioned, for a launch date foreseen at the 2024-2025 horizon.

Published
2019

7. Impact of the North Equatorial Current meandering on a pelagic ecosystem: a modeling approach

Author

Dadou, I., Garcon, V., Anderson, V., Flierl, G.R., and David, C.S.

Subjects
Atlantic Ocean -- Environmental aspects, Ocean currents -- Analysis, Eddies -- Research, Phytoplankton -- Research, Marine ecology -- Atlantic Ocean, Biological sciences, Earth sciences
Abstract

North Equatorial Current (NEC) meandering causes disturbances to the planktonic populations and to the biological pump efficiency despite the simple feature of the pelagic ecosystem models. Mesoscale hydrographic differences in significantly affect the biological dynamics in the NEC. Baroclinic instabilities lead to the formation of eddies and meanders, which causes upward motion of water transporting nitrogen into the euphotic layer. The transported nitrogen increases the production and biomass of phytoplankton.

Published
1996

9. INDO-FRENCH HIGH-RESOLUTION THERMAL INFRARED SPACE MISSION FOR EARTH NATURAL RESOURCES ASSESSMENT AND MONITORING – CONCEPT AND DEFINITION OF TRISHNA

Author

Lagouarde, J.-P., primary, Bhattacharya, B. K., additional, Crébassol, P., additional, Gamet, P., additional, Adlakha, D., additional, Murthy, C. S., additional, Singh, S. K., additional, Mishra, M., additional, Nigam, R., additional, Raju, P. V., additional, Babu, S. S., additional, Shukla, M. V., additional, Pandya, M. R., additional, Boulet, G., additional, Briottet, X., additional, Dadou, I., additional, Dedieu, G., additional, Gouhier, M., additional, Hagolle, O., additional, Irvine, M., additional, Jacob, F., additional, Kumar, K. K, additional, Laignel, B., additional, Maisongrande, P., additional, Mallick, K., additional, Olioso, A., additional, Ottlé, C., additional, Roujean, J.-L., additional, Sobrino, J., additional, Ramakrishnan, R., additional, Sekhar, M., additional, and Sarkar, S. S., additional

Published
2019
Full Text
View/download PDF

10. Reconstruction of super-resolution ocean pCO2 and air–sea fluxes of CO2 from satellite imagery in the southeastern Atlantic

Author

Hernandez-Carrasco, I., Sudre, J., Garcon, V., Yahia, H., Garbe, C., Paulmier, Aurélien, Dewitte, Boris, Illig, Serena, Dadou, I., Gonzalez-Davila, M., and Santana-Casiano, J. M.

Subjects
lcsh:Geology, lcsh:QH501-531, lcsh:QH540-549.5, lcsh:QE1-996.5, lcsh:Life, lcsh:Ecology, Physics::Atmospheric and Oceanic Physics
Abstract

An accurate quantification of the role of the ocean as source/sink of greenhouse gases (GHGs) requires to access the high-resolution of the GHG air–sea flux at the interface. In this paper we present a novel method to reconstruct maps of surface ocean partial pressure of CO2 ( pCO2) and air–sea CO2 fluxes at super resolution (4 km, i.e., 1/32° at these latitudes) using sea surface temperature (SST) and ocean color (OC) data at this resolution, and CarbonTracker CO2 fluxes data at low resolution (110 km). Inference of super-resolution pCO2 and air–sea CO2 fluxes is performed using novel nonlinear signal processing methodologies that prove efficient in the context of oceanography. The theoretical background comes from the microcanonical multifractal formalism which unlocks the geometrical determination of cascading properties of physical intensive variables. As a consequence, a multi-resolution analysis performed on the signal of the so-called singularity exponents allows for the correct and near optimal cross-scale inference of GHG fluxes, as the inference suits the geometric realization of the cascade. We apply such a methodology to the study offshore of the Benguela area. The inferred representation of oceanic partial pressure of CO2 improves and enhances the description provided by CarbonTracker, capturing the small-scale variability. We examine different combinations of ocean color and sea surface temperature products in order to increase the number of valid points and the quality of the inferred pCO2 field. The methodology is validated using in situ measurements by means of statistical errors. We find that mean absolute and relative errors in the inferred values of pCO2 with respect to in situ measurements are smaller than for CarbonTracker.

Published
2015

12. The Indian-French Trishna Mission: Earth Observation in the Thermal Infrared with High Spatio-Temporal Resolution

Author

Lagouarde, J.-P., primary, Bhattacharya, B.K., additional, Crebassol, P., additional, Gamet, P., additional, Babu, S. S., additional, Boulet, G., additional, Briottet, X, additional, Buddhiraju, K.M., additional, Cherchali, S., additional, Dadou, I., additional, Dedieu, G., additional, Gouhier, M., additional, Hagolle, O., additional, Irvine, M., additional, Jacob, F., additional, Kumar, A., additional, Kumar, K. K., additional, Laignel, B., additional, Mallick, K., additional, Murthy, C.S., additional, Olioso, A., additional, Ottle, C., additional, Pandya, M. R., additional, Raju, P. V., additional, Roujean, J.-L., additional, Sekhar, M., additional, Shukla, M. V., additional, Singh, S. K., additional, Sobrino, J., additional, and Ramakrishnan, R., additional

Published
2018
Full Text
View/download PDF

13. Interannual variability in the South-East Atlantic Ocean, focusing on the Benguela Upwelling System : remote versus local forcing

Author

Bachelery, M. L., Illig, Serena, and Dadou, I.

Subjects
experimentation, interannual variability model, local atmospheric forcing, Benguela Upwelling System, equatorial connexion, coastal-trapped waves
Abstract

We investigate the respective roles of equatorial remote (Equatorial Kelvin Waves) and local atmospheric (wind, heat fluxes) forcing on coastal variability in the South-East Atlantic Ocean extending up to the Benguela Upwelling System (BUS) over the 2000-2008 period. We carried out a set of six numerical experiments based on a regional ocean model, that differ only by the prescribed forcing (climatological or total) at surface and lateral boundaries. Results show that at subseasonal timescales (

Published
2016

14. Forcings of nutrient, oxygen, and primary production interannual variability in the southeast Atlantic Ocean

Author

Bachelery, M. L., Illig, Serena, and Dadou, I.

Subjects
interannual variability, Benguela Upwelling System, biogeochemical cycles, remote equatorial forcing, primary production
Abstract

The recurrent occurrences of interannual warm and cold events along the coast of Africa have been intensively studied because of their striking effects on climate and fisheries. Using sensitivity experimentation based on a coupled physical/biogeochemical model, we show that the oceanic remote equatorial forcing explains more than 85% of coastal interannual nitrate and oxygen fluctuations along the Angolan and Namibian coasts up to the Benguela Upwelling System (BUS). These events, associated with poleward propagations of upwelling and downwelling Coastal Trapped Waves (CTW), are maximum in subsurface and controlled by physical advection processes. Surprisingly, an abrupt change in the CTW biogeochemical signature is observed in the BUS, associated with mixed vertical gradients due to the strong local upwelling dynamics. Coastal modifications of biogeochemical features result in significant primary production variations that may affect fisheries habitats and coastal biodiversity along the southwestern African coasts and in the BUS.

Published
2016

15. Using JGOFS in situ and ocean color data to compare biogeochemical models and estimate their parameters in the subtropical North Atlantic Ocean

Author

Dadou, I., Evans, G., and Garcon, V.

Subjects
North Atlantic Ocean -- Environmental aspects, Atmospheric carbon dioxide -- Structure, Atmospheric carbon dioxide -- Research, Atmospheric research, Biological sciences, Earth sciences
Abstract

Relevance of a biogeochemical dataset in deciding the candidate models and estimating the parameters for three different models of biological nitrogen flux in a water column is analyzed by using the data from the French JGOFS EUMELI cruises and the SeaEiFS ocean color sensor. The model with dissolved organic matter exhibited reasonable annual behavior and possible role of deep nitrate data was seen due to large seasonal changes in deep nitrate data.

Published
2004

16. Variability of the biological front south of Africa from SeaWiFS and a coupled physical-biological model

Author

Llido, J., Machu, E., Sudre, J., Dadou, I., and Garcon, V.

Subjects
Marine phytoplankton -- Environmental aspects, Marine phytoplankton -- Research, Ocean circulation -- Environmental aspects, Ocean circulation -- Observations, Climatic changes -- Environmental aspects, Biological sciences, Earth sciences
Abstract

Spatio-temporal variability of the biological front in the Agulhas Current system comparing SeaWiFS and modeled chlorophyll fields produced by the monthly atmospheric NCEP reanalysis over a period of four years October 1997 to October 2001is examined. The model reproduces the annual cycle of the observed chlorophyll within the Agulhas Current system biogeochemical province and the modeled fields display slightly higher annual mean and amplitude.

Published
2004

17. Reconstruction of super-resolution ocean pCO 2 and air-sea fluxes of CO 2 from satellite imagery in the Southeastern Atlantic

Author

Hernández-Carrasco, Ismael, Sudre, Joël, Garçon, Véronique, Paulmier, A, Dewitte, B, Illig, S, Dadou, I, Yahia, Hussein, Garbe, Christoph, González-Dávila, M, Santana Casiano, J.M., Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), DYNBIO LEGOS, Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Geometry and Statistics in acquisition data (GeoStat), Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Interdisciplinary Center for Scientific Computing (IWR), Universität Heidelberg [Heidelberg] = Heidelberg University, Instituto de Oceanografía y Cambio Global (IOCAG), Université de Las Palmas de Gran Canaria [Espagne] (ULPGC), ESA Support To Science Element Grant N◦ 400014715/11/I-NB OceanFlux- Upwelling Theme, SOLAS, SOCAT, IOCCP, IMBER, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Universität Heidelberg [Heidelberg]

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Green House Gases, Ocean/Atmosphere, [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, [SDE.MCG]Environmental Sciences/Global Changes, [INFO.INFO-IR]Computer Science [cs]/Information Retrieval [cs.IR], [NLIN.NLIN-CD]Nonlinear Sciences [physics]/Chaotic Dynamics [nlin.CD], Multiscale Image Analysis, Wavelet Analysis, Climate change, Climate budget, Turbulence and coherent structures, Superresolution
Abstract

This work is a contribution to ESA Support To Science Element Grant N◦ 400014715/11/I-NB OceanFlux- Upwelling Theme. The Surface Ocean CO2 Atlas (SOCAT) is an international effort, supported by the International Ocean Carbon Coordination Project (IOCCP), the Surface Ocean Lower Atmo- sphere Study (SOLAS), and the Integrated Marine Biogeochem- istry and Ecosystem Research program (IMBER), to deliver a uni- formly quality-controlled surface ocean CO2 database. The many researchers and funding agencies responsible for the collection of data and quality control are thanked for their contributions to SO- CAT; International audience; An accurate quantification of the role of the ocean as source/sink of Green House Gases (GHGs) requires to access the high-resolution of the GHG air-sea flux at the interface. In this paper we present a novel method to reconstruct maps of surface ocean partial pressure of CO 2 (pCO 2) and 5 air-sea CO 2 fluxes at super resolution (4 km) using Sea Surface Temperature (SST) and Ocean Colour (OC) data at this resolution, and CarbonTracker CO 2 fluxes data at low resolution (110 km). Inference of super-resolution of pCO 2 , and air-sea CO 2 fluxes is performed using novel nonlinear signal 10 processing methodologies that prove efficient in the context of oceanography. The theoretical background comes from the Microcanonical Multifractal Formalism which unlocks the geometrical determination of cascading properties of physical intensive variables. As a consequence, a multiresolution 15 analysis performed on the signal of the so-called singularity exponents allows the correct and near optimal cross-scale inference of GHGs fluxes, as the inference suits the geometric realization of the cascade. We apply such a methodology to the study offshore of the Benguela area. The inferred rep-20 resentation of oceanic partial pressure of CO 2 improves and enhances the description provided by CarbonTracker, capturing the small scale variability. We examine different combinations of Ocean Colour and Sea Surface Temperature products in order to increase the number of valid points and the 25 quality of the inferred pCO 2 field. The methodology is validated using in-situ measurements by means of statistical errors. We obtain that mean absolute and relative errors in the inferred values of pCO 2 with respect to in-situ measurements are smaller than for CarbonTracker.

Published
2015

18. Validation of inferred high resolution ocean pCO2 and air-sea fluxes with in-situ and remote sensing data

Author

Hernandez-Carrasco, Ismael, Sudre, J, Garcon, Veronique, Yahia, Hussein, Dewitte, Boris, Garbe, Christoph, Illig, Serena, Montès, Ivonne, Paulmier, A., Dadou, I., Butz, A., Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Systèmes complexes couplés (SYSCO2), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Geometry and Statistics in acquisition data (GeoStat), Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Echanges Côte-Large (ECOLA), Interdisciplinary Center for Scientific Computing (IWR), Universität Heidelberg [Heidelberg], Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), Institute for Anthropomatics (KIT), Karlsruhe Institute of Technology (KIT), ESA OceanFlux., ESA-ESRIN, Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Universität Heidelberg [Heidelberg] = Heidelberg University

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, [NLIN.NLIN-CD]Nonlinear Sciences [physics]/Chaotic Dynamics [nlin.CD], Physics::Atmospheric and Oceanic Physics
Abstract

International audience; -resolution ocean pCO2 and air-sea CO2 fluxes with in-situ and remote sensing data a) Introduction Submesocale activity is being recognized as of primary importance in global ocean processes such as for instance the precise determination of GHGs exchanges between the ocean and the atmosphere. The scarcity of oceanographic cruises and the lack of available satellite products for GHG concentrations at high resolution prevent from obtaining a global assessment of their spatial variability at small scales. In this ESA Oceanflux project, the teams are making use of non-linear signal processing methods for inferring super-resolution maps (pixels resolution: 4kms) of CO2 fluxes by setting up a novel methodology based on the determination of an optimal multiresolution analysis computed from singularity exponents associated to Sea Surface Temperature (SST), chlorophyl concentration and low resolution CO2 fluxes. The multiresolution analysis makes use of (MERIS, MODIS AVW-MERGED and GSM-MERGED products. We present validation experiments using in-situ boat campaigns data colocalized with the generated high resolution products. Validation has been performed in Benguela OMZ region. b) Method SIngularity exponents are important non-linear and multiscale characteristics of turbulent data [1, 2, 3]. They can be used to set up optimal inference across the scales of complex signals [4]. In this work, seasonal regression coefficients are computed from ROMS simulation outputs. We have been using globcolour merged products (AVW and GSM) for ocean colour to: increase the number of points in the ocean pCO2 field, to get more intersections for a wider validation for in-situ pCO2. We have also made comparison of inferred pCO2 from Globcolour with those from MERIS. In AVW CHL_a values are weighted by the relative error for each sensor on the simple averaging. In GSM we use fully normalized water leaving radiances. c) Results The validation analysis shows that values of superresolution pCO2 are closer to insitu pCO2 when we use merged ocean color (closer with GSM globcolour) . Analysis of the PDFs of pCO2 values show good agreement between inferred pCO2 and CarbonTracker (better for merged products). From singularity spectra analysis we obtain that the merged products improve the representation of the transition fronts (binomial cascade behaviour at small values of the singularity exponents). d) Discussion & Conclusion The methodology introduced in the ESA Oceanflux proposal is able to derive super resolution maps of GHGs fluxes validated by in-situ boat campaigns with excellents results which in particular are outperforming the outputs of simulation models such as CarbonTracker: not only the resolution, but the data itself is closer to in-situ data. As a consequence, the methodology presented in the ESA Oceanflux will serve as a tool for better quantitative evazluation of GHGs fluxes betwwen the ocean and the atmosphere. Bibliography [1] I. Inference of super-resolution ocean pCO2 and air-sea CO2 fluxes from non-linear and multiscale processing methods

Published
2014

19. Inference of super-resolution ocean pCO2 and air-sea CO2 fluxes from non-linear and multiscale processing methods

Author

Hernandez-Carrasco, Ismael, Sudre, J., Garçon, Veronique, Yahia, Hussein, Dewitte, Boris, Garbe, Christoph, Illig, Serena, Montes, Ivonne, Dadou, I., Paulmier, Aurélien, Butz, André, Laboratoire d'Etudes en Géophysique et Océanographie Spatiales (LEGOS NOUMEA), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR065-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), DYNBIO LEGOS, Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Geometry and Statistics in acquisition data (GeoStat), Inria Bordeaux - Sud-Ouest, Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria), Echanges Côte-Large (ECOLA), Image Processing and Modeling, Interdisciplinary Center for Scientific Computing (IWR), Universität Heidelberg [Heidelberg]-Universität Heidelberg [Heidelberg], Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), Karlsruhe Institute of Technology (KIT), European Geophysical Union, Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Universität Heidelberg [Heidelberg] = Heidelberg University-Universität Heidelberg [Heidelberg] = Heidelberg University

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], [SDE.MCG]Environmental Sciences/Global Changes, [NLIN.NLIN-CD]Nonlinear Sciences [physics]/Chaotic Dynamics [nlin.CD], [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, Physics::Atmospheric and Oceanic Physics
Abstract

International audience; In recent years the role of submesoscale activity is emerging as being more and more important to understand global ocean properties, for instance, for accurately estimating the sources and sinks of Greenhouse Gases (GHGs) at the air-sea interface. The scarcity of oceanographic cruises and the lack of available satellite products for GHG concentrations at high resolution prevent from obtaining a global assessment of their spatial variability at small scales. In this work we develop a novel method to reconstruct maps of CO2 fluxes at super resolution (4km) using SST and ocean colour data at this resolution, and CarbonTracker CO2 fluxes data at low resolution (110 km). The responsible process for propagating the information between scales is related to cascading properties and multiscale organization, typical of fully developed turbulence. The methodology, based on the Microcanonical Multifractal Formalism, makes use, from the knowledge of singularity exponents, of the optimal wavelet for the determination of the energy injection mechanism between scales. We perform a validation analysis of the results of our algorithm using pCO2 ocean data from in-situ measurements in the upwelling region of Namibia.

Published
2014

21. Hypoxia In The Lower St. Lawrence Estuary: How Physics Controls Spatial Patterns

Author

Lefort, S., Gratton, Y., Mucci, A., Dadou, I., Gilbert, D., GEOTOP and Department of Earth and Planetary Sciences, McGill University = Université McGill [Montréal, Canada], Centre Eau Terre Environnement [Québec] (INRS - ETE), Institut National de la Recherche Scientifique [Québec] (INRS), DYNBIO LEGOS, Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Fisheries and Oceans Canada, Maurice Lamontagne Institute, Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, ORGANIC-MATTER, UPWELLING SYSTEM, GULF, RESPIRATORY ACTIVITY, BOTTOM WATERS, GEOCHEMICAL EVIDENCE, TROUGH, LAURENTIAN, COASTAL OCEAN, CARBON BUDGET, OXYGEN
Abstract

ISI Document Delivery No.: 980RD Times Cited: 1 Cited Reference Count: 57 Cited References: Anschutz P, 2000, GEOCHIM COSMOCHIM AC, V64, P2751, DOI 10.1016/S0016-7037(00)00400-2 Benoit P, 2006, MAR CHEM, V102, P13, DOI 10.1016/j.marchem.2005.09.015 Bograd SJ, 2008, GEOPHYS RES LETT, V35, DOI 10.1029/2008GL034185 Bugden G.L., 1991, CANADIAN SPECIAL PUB, V113, P139 CHAPMAN DC, 1985, J PHYS OCEANOGR, V15, P1060, DOI 10.1175/1520-0485(1985)0152.0.CO;2 Cloern JE, 2001, MAR ECOL PROG SER, V210, P223, DOI 10.3354/meps210223 Colombo JC, 1996, MAR CHEM, V51, P277, DOI 10.1016/0304-4203(95)00059-3 Colombo JC, 1996, MAR CHEM, V51, P295, DOI 10.1016/0304-4203(95)00060-7 Craig J, 2008, AZMP B PMZA, V7, P37 Czeschel R, 2011, J GEOPHYS RES-OCEANS, V116, DOI 10.1029/2010JC006565 Diaz R. J., 2009, HYPOXIA, P1, DOI 10.1016/S1546-5098(08)00001-0 Diaz RJ, 2001, J ENVIRON QUAL, V30, P275 Dickie L.M., 1983, ESTUARIES ENCLOSED S, P403 Galbraith PS, 2006, J GEOPHYS RES-OCEANS, V111, DOI 10.1029/2005JC003159 Genovesi L, 2011, LIMNOL OCEANOGR, V56, P1319, DOI 10.4319/lo.2011.56.4.1319 Gilbert D, 2005, LIMNOL OCEANOGR, V50, P1654 Gilbert D., 2004, ICES ANN SCI C INT C Gilbert D, 2010, BIOGEOSCIENCES, V7, P2283, DOI 10.5194/bg-7-2283-2010 Gilbert D, 1997, CAN J FISH AQUAT SCI, V54, P57, DOI 10.1139/cjfas-54-S1-57 GLUD RN, 1994, DEEP-SEA RES PT I, V41, P1767 Grasshoff K, 1999, METHODS SEAWATER ANA, DOI DOI 10.1002/9783527613984 GRATTON Y, 1988, J GEOPHYS RES-OCEANS, V93, P6947, DOI 10.1029/JC093iC06p06947 Gutknecht E., 2011, BIOGEOSCI DISCUSS, V8, P3537, DOI DOI 10.5194/BGD-8-3537-2011 Han GQ, 1999, J PHYS OCEANOGR, V29, P1279, DOI 10.1175/1520-0485(1999)0292.0.CO;2 Johnson C., 1987, NUMERICAL SOLUTION P Katsev S, 2007, LIMNOL OCEANOGR, V52, P2555, DOI 10.4319/lo.2007.52.6.2555 Koutitonsky V. G., 1991, CAN SPEC PUBL FISH A, V113, P139 LARGE WG, 1994, REV GEOPHYS, V32, P363, DOI 10.1029/94RG01872 LeBlond P. H., 1978, WAVES OCEAN LEDWELL JR, 1993, NATURE, V364, P701, DOI 10.1038/364701a0 Lehmann MF, 2009, LIMNOL OCEANOGR, V54, P2157, DOI 10.4319/lo.2009.54.6.2157 LUCOTTE M, 1991, ESTUAR COAST SHELF S, V32, P297, DOI 10.1016/0272-7714(91)90022-4 Matear RJ, 2003, GLOBAL BIOGEOCHEM CY, V17, DOI 10.1029/2002GB001997 Mathworks Inc, 2006, PART DIFF EQ TOOLB U Mohrholz V, 2008, CONT SHELF RES, V28, P424, DOI 10.1016/j.csr.2007.10.001 Monteiro PMS, 2011, ENVIRON RES LETT, V6, DOI 10.1088/1748-9326/6/2/025002 Monteiro PMS, 2008, DEEP-SEA RES PT I, V55, P435, DOI 10.1016/j.dsr.2007.12.010 Monteiro PMS, 2006, GEOPHYS RES LETT, V33, DOI 10.1029/2006GL026234, Monteiro PMS, 1999, ESTUAR COAST SHELF S, V49, P877, DOI 10.1006/ecss.1999.0550 Muzuka ANN, 1999, MAR GEOL, V160, P251, DOI 10.1016/S0025-3227(99)00022-5 Ozsoy E, 1997, EARTH-SCI REV, V42, P231, DOI 10.1016/S0012-8252(97)81859-4 Packard T.T., 1985, Advances in Aquatic Microbiology, V3, P207 Pena MA, 2010, BIOGEOSCIENCES, V7, P933 Saucier FJ, 2003, J GEOPHYS RES-OCEANS, V108, DOI 10.1029/2000JC000686 SAVENKOFF C, 1995, CONT SHELF RES, V15, P613, DOI 10.1016/0278-4343(94)00041-K Savenkoff C, 2001, ESTUAR COAST SHELF S, V52, P565, DOI 10.1006/ecss.2001.0774 Savenkoff C, 1996, CAN J FISH AQUAT SCI, V53, P2451, DOI 10.1139/cjfas-53-11-2451 Sherwood OA, 2011, P NATL ACAD SCI USA, V108, P1011, DOI 10.1073/pnas.1004904108 Silverberg N, 2000, DEEP-SEA RES PT II, V47, P699, DOI 10.1016/S0967-0645(99)00123-X Smith GC, 2006, J PHYS OCEANOGR, V36, P1485, DOI 10.1175/JPO2927.1 Smith JN, 1999, LIMNOL OCEANOGR, V44, P207 Taylor KE, 2001, J GEOPHYS RES-ATMOS, V106, P7183, DOI 10.1029/2000JD900719 TEE KT, 1989, J GEOPHYS RES-OCEANS, V94, P8075, DOI 10.1029/JC094iC06p08075 Thibodeau B, 2010, GEOPHYS RES LETT, V37, DOI 10.1029/2010GL044771 Thibodeau B, 2006, MAR GEOL, V231, P37, DOI 10.1016/j.margeo.2006.05.010 VOSJAN JH, 1987, LIMNOL OCEANOGR, V32, P767 VOSJAN JH, 1990, NETH J SEA RES, V25, P89, DOI 10.1016/0077-7579(90)90011-5 Lefort, S. Gratton, Y. Mucci, A. Dadou, I. Gilbert, D. Gilbert, Denis/A-3067-2010 Gilbert, Denis/0000-0002-9554-9594 NSERC Strategic grant; DFO CCSI (Climate Change Science Initiative) grant; Department of Earth and Planetary Sciences/McGill; GEOTOP-UQAM-McGill research center; LEGOS laboratory; University of Toulouse III (Paul Sabatier, France) This research was funded by a NSERC Strategic grant to A.M., D.G. and Y.G, and a DFO CCSI (Climate Change Science Initiative) grant to D.G. Additional financial support to S.L. was provided by the Department of Earth and Planetary Sciences/McGill, the GEOTOP-UQAM-McGill research center, the LEGOS laboratory and the University of Toulouse III (Paul Sabatier, France). We thank the captains and crew of R/V Alcide C. Horth and R/V Coriolis II for their help during the numerous cruises between 2002 and 2011. We acknowledge the two anonymous reviewers for their insightful comments. 1 AMER GEOPHYSICAL UNION WASHINGTON J GEOPHYS RES-OCEANS; A laterally integrated advection-diffusion two-dimensional model was implemented to simulate the spatial distribution of dissolved oxygen and the development of hypoxic conditions in the deep waters of the Laurentian Channel (Estuary and Gulf of St. Lawrence, Eastern Canada). Our simulations reveal that the horizontal distribution of dissolved oxygen in the bottom waters of the Laurentian Channel is determined by a combination of physical and biogeochemical processes, whereas its vertical distribution is governed by the deep water circulation. This result strongly suggests that the physics of the system and the source water properties are mostly responsible for the generation of a mid-water column oxygen minimum and the oxygen distribution pattern in the deep water column.

Published
2012
Full Text
View/download PDF

22. Reconstruction of super-resolution ocean <i>p</i>CO<sub>2</sub> and air–sea fluxes of CO<sub>2</sub> from satellite imagery in the southeastern Atlantic

Author

Hernández-Carrasco, I., primary, Sudre, J., additional, Garçon, V., additional, Yahia, H., additional, Garbe, C., additional, Paulmier, A., additional, Dewitte, B., additional, Illig, S., additional, Dadou, I., additional, González-Dávila, M., additional, and Santana-Casiano, J. M., additional

Published
2015
Full Text
View/download PDF

24. Interpretation of the nitrogen isotopic signal variations in the Mauritanian upwelling with a 2D physical-biogeochemical model

Author

Giraud, X., Bertrand, P., Garcon, V., Dadou, I., Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Télescope Bernard Lyot (TBL), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU]Sciences of the Universe [physics]
Abstract

International audience; A physical-biogeochemical model is used to simulate the evolution of the δ15N signal during the last glacial-interglacial transition in sedimentary cores offshore from the Mauritanian upwelling. The biological model is a classical nitrogen-based trophic chain model, which also computes the nitrogen isotope fractionation. The 2D physical primitive equation model simulates the coastal upwelling circulation and is applied for different sea level scenarios. The effect of the sea level rise, inducing the shelf immersion, seems to be a main factor explaining the organic nitrogen flux and isotopic signal variations along the last deglaciation. This effect is modulated by an upwelling seasonality that may have been much longer at the Last Glacial Maximum, around 10-11 months instead of 4-5 months at present. Between 15 and 5.5 kyr ago, 60% of the sedimentary δ15N variations could be explained by this local shelf immersion effect. This reconstruction also reproduces the strong isotopic fall occurring between 5.5 kyr and the present.

Published
2003
Full Text
View/download PDF

25. Coupled physical/biogeochemical modeling including O2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

Author

Gutknecht, E., Dadou, I., Le Vu, B., Cambon, G., Sudre, J., Garçon, V., Machu, E., Rixen, T., Kock, A., Flohr, A., Paulmier, A., Lavik, G., Gutknecht, E., Dadou, I., Le Vu, B., Cambon, G., Sudre, J., Garçon, V., Machu, E., Rixen, T., Kock, A., Flohr, A., Paulmier, A., and Lavik, G.

Abstract

The Eastern Boundary Upwelling Systems (EBUS) contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs), EBUS represent key regions for the oceanic nitrogen (N) cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O) occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial due to anticipated changes in the winds, productivity, and oxygen content. We developed a biogeochemical model (BioEBUS) taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic coupled physical/biogeochemical configuration in the Namibian upwelling system (northern Benguela) using the high-resolution hydrodynamic ROMS model. We present here a validation using in situ and satellite data as well as diagnostic metrics and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate, and chlorophyll a concentrations, and the rates of microbial processes (e.g, NH4+ and NO2− oxidation, NO3− reduction, and anammox) as well. Based on our sensitivity analyses, biogeochemical parameter values associated with organic matter decomposition, vertical sinking, and nitrification play a key role for the low-oxygen water content, N loss, and N2O concentrations in the OMZ. Moreover, the explicit parameterization of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is necessary to improve the representation of microbial activity linked with the OMZ. The simulated minimum oxygen concentrations are driven by th

Published
2013

26. Nitrogen transfers off Walvis Bay: a 3-D coupled physical/biogeochemical modeling approach in the Namibian upwelling system

Author

Gutknecht, E., Dadou, I., Marchesiello, P., Cambon, G., Le Vu, B., Sudre, J., Garçon, V., Machu, E., Rixen, T., Kock, A., Flohr, A., Paulmier, A., Lavik, G., Gutknecht, E., Dadou, I., Marchesiello, P., Cambon, G., Le Vu, B., Sudre, J., Garçon, V., Machu, E., Rixen, T., Kock, A., Flohr, A., Paulmier, A., and Lavik, G.

Abstract

Eastern boundary upwelling systems (EBUS) are regions of high primary production often associated with oxygen minimum zones (OMZs). They represent key regions for the oceanic nitrogen (N) cycle. By exporting organic matter (OM) and nutrients produced in the coastal region to the open ocean, EBUS can play an important role in sustaining primary production in subtropical gyres. However, losses of fixed inorganic N through denitrification and anammox processes take place in oxygen depleted environments such as EBUS, and can potentially mitigate the role of these regions as a source of N to the open ocean. EBUS can also represent a considerable source of nitrous oxide (N2O) to the atmosphere, affecting the atmospheric budget of N2O. In this paper a 3-D coupled physical/biogeochemical model (ROMS/BioEBUS) is used to investigate the N budget in the Namibian upwelling system. The main processes linked to EBUS and associated OMZs are taken into account. The study focuses on the northern part of the Benguela upwelling system (BUS), especially the Walvis Bay area (between 22° S and 24° S) where the OMZ is well developed. Fluxes of N off the Walvis Bay area are estimated in order to understand and quantify (1) the total N offshore export from the upwelling area, representing a possible N source that sustains primary production in the South Atlantic subtropical gyre; (2) export production and subsequent losses of fixed N via denitrification and anammox under suboxic conditions (O2 < 25 mmol O2 m−3); and (3) the N2O emission to the atmosphere in the upwelling area. In the mixed layer, the total N offshore export is estimated as 8.5 ± 3.9 × 1010 mol N yr−1 at 10° E off the Walvis Bay area, with a mesoscale contribution of 20%. Extrapolated to the whole BUS, the coastal N source for the subtropical gyre corresponds to 0.1 ± 0.04 mol N m−2 yr−1. This N flux represents a major source of N for the gyre compared with other N sources, and contributes 28% of the new primary production e

Published
2013

27. Modeling delta(15)N evolution: First palaeoceanographic applications in a coastal upwelling system

Author

GIRAUD, Xavier, Bertrand, P, Garcon, V, Dadou, I, UMR 5805 Environnements et Paléoenvironnements Océaniques et Continentaux (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography
Abstract

The delta(15)N Signal in marine sediments appears to be a good palaeoceanographic tracer. It records biological processes in the water column and is transferred to and preserved in the sediments. Changes in forcing factors in upwelling systems may be recorded by delta(15)N. These forcing conditions can be of a biogeochemical nature, such as the initial isotopic signal of the nutrients or the trophic structure, or of a physical nature, such as wind stress, insolation, temperature or dynamic recycling. A simple nitrogen-based trophic chain model was used to follow the development of the nitrogen isotopic signal in nutrients, phytoplankton, zooplankton and detritus. Detrital delta(15)N, influenced by the isotopic signature of the upwelled nutrients and isotopic fractionation along the trophic chain (photosynthesis and zooplankton excretion), was then compared to the sedimentary signal measured off Mauritania. In our model, the biological variables are transported at shallow depths by a simple circulation scheme perpendicular to the coast depicting a continental shelf recirculation cell. Because cell length depends on the extension of the continental shelf, modifications of the cell length mimic sea level changes. Long cell length (high sea lever) scenarios produce higher delta(15)N values whereas short cell length scenarios result in lower values as in the glacial low sea level periods. Despite changes in many climatic parameters throughout this period, our results show that changing the sea level is sufficient to reconstruct the main pattern of the sedimentary delta(15)N variations offshore of the Mauritanian upwelling, i.e. an increase from about 3 parts per thousand to 7 parts per thousand during the deglaciation, without invoking any change in nitrogen fixation or denitrification.

Published
2000
Full Text
View/download PDF

29. Influence of Rossby waves on primary production from a coupled physical-biogeochemical model in the North Atlantic Ocean

Author

Charria, G., Dadou, I., Cipollini, P., Drevillon, M., Garcon, V., Charria, G., Dadou, I., Cipollini, P., Drevillon, M., and Garcon, V.

Abstract

Rossby waves appear to have a clear signature on surface chlorophyll concentrations which can be explained by a combination of vertical and horizontal mechanisms. In this study, we investigate the role of the different physical processes in the north Atlantic to explain the surface chlorophyll signatures and the consequences on primary production, using a 3-D coupled physical/biogeochemical model for the year 1998. The analysis at 20 given latitudes, mainly located in the subtropical gyre, where Rossby waves are strongly correlated with a surface chlorophyll signature, shows the important contribution of horizontal advection and of vertical advection and diffusion of inorganic dissolved nitrogen. The main control mechanism differs according to the biogeochemical background conditions of the area. The surface chlorophyll anomalies, induced by these physical mechanisms, have an impact on primary production. We estimate that Rossby waves induce, locally in space and time, increases (generally associated with the chlorophyll wave crest) and decreases (generally associated with the chlorophyll wave trough) in primary production, ±20% of the estimated background primary production. This symmetrical situation suggests a net weak effect of Rossby waves on primary production.

Published
2008

30. Importance of dissolved organic nitrogen in the north Atlantic Ocean in sustaining primary production: a 3-D modelling approach

Author

Charria, G., Dadou, I., Llido, J., Drevillon, M., Garcon, V., Charria, G., Dadou, I., Llido, J., Drevillon, M., and Garcon, V.

Abstract

An eddy-permitting coupled ecosystemcirculation model including dissolved organic matter is used to estimate the dissolved organic nitrogen (DON) supply sustaining primary production in the subtropical north Atlantic Ocean. After an analysis of the coupled model performances compared to the data, a sensitivity study demonstrates the strong impact of parameter values linked to the hydrolysis of particulate organic nitrogen and remineralisation of dissolved organic nitrogen on surface biogeochemical concentrations. The physical transport of dissolved organic nitrogen contributes to maintain the level of primary production in this subtropical gyre. It is dominated by the meridional component. We estimate a meridional net input of 0.039 molNm−2 yr−1 over the domain (13–35 N and 71– 40 W) in the subtropical gyre. This supply is driven by the Ekman transport in the southern part and by non-Ekman transport (meridional current components, eddies, meanders and fronts) in the northern part of the subtropical gyre. At 12 N, our estimate (18 kmolN s−1) confirms the estimation (17.9 kmolN s−1) made by Roussenov et al. (2006) using a simplified biogeochemical model in a large scale model. This DON meridional input is within the range (from 0.05 up to 0.24 molNm−2 yr−1) (McGillicuddy and Robinson, 1997; Oschlies, 2002) of all other possible mechanisms (mesoscale activity, nitrogen fixation, atmospheric deposition) fuelling primary production in the subtropical gyre. The present study confirms that the lateral supply of dissolved organic nitrogen might be important in closing the N budget over the north Atlantic Ocean and quantifies the importance of meridional input of dissolved organic nitrogen.

Published
2008

32. Coupled physical/biogeochemical modeling including O&lt;sub&gt;2&lt;/sub&gt;-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

Author

Gutknecht, E., primary, Dadou, I., additional, Le Vu, B., additional, Cambon, G., additional, Sudre, J., additional, Garçon, V., additional, Machu, E., additional, Rixen, T., additional, Kock, A., additional, Flohr, A., additional, Paulmier, A., additional, and Lavik, G., additional

Published
2013
Full Text
View/download PDF

33. Influence of Rossby waves on primary production from a coupled physical-biogeochemical model in the North Atlantic Ocean

Author

Charria, G., Dadou, I., Cipollini, P., Drevillon, M., Garcon, V., Charria, G., Dadou, I., Cipollini, P., Drevillon, M., and Garcon, V.

Abstract

How do Rossby waves influence primary production in the North Atlantic Ocean? Rossby waves have a clear signature on surface chlorophyll concentrations which can be explained by a combination of vertical and horizontal mechanisms (reviewed in Killworth et al., 2004). In this study, we aim to investigate the role of the different physical processes to explain the surface chlorophyll signatures and the consequences on primary production using a 3-D coupled physical/biogeochemical model for the year 1998. The analysis at 20 given latitudes, mainly located in the subtropical gyre, where Rossby waves are strongly correlated with a surface chlorophyll signature, shows that vertical and horizontal processes are involved in the surface chlorophyll anomalies. Furthermore, the ecosystem response is, as expected, stronger when vertical input of dissolved inorganic nitrogen is observed. The surface chlorophyll anomalies, induced by these physical mechanisms, have an impact on primary production. We then estimate that Rossby waves induce, locally in space and time, increases (generally associated with the wave crest) and decreases (generally associated with the wave trough) in primary production (±20% of the estimated primary production). This symmetrical situation suggests a net weak effect of Rossby waves on primary production.

Published
2007

34. Understanding the influence of Rossby waves on surface chlorophyll concentrations in the North Atlantic Ocean

Author

Charria, G., Dadou, I., Cipollini, P., Drevillon, M., De Mey, P., Garcon, V., Charria, G., Dadou, I., Cipollini, P., Drevillon, M., De Mey, P., and Garcon, V.

Abstract

The variability (in space and time) of westward propagating Rossby waves is analyzed with a wavelet method between 10N and 40N in the North Atlantic Ocean using two remotely sensed data sets (Sea Level Anomalies – SLA and surface chlorophyll-a concentrations) in order to better understand the waves' characteristics and their impacts on the chlorophyll distribution. Signals with wavelengths between ∼ 500 km and ∼ 1000 km with ∼ 4- to ∼ 24-month periods were detected and identified as the first baroclinic mode of Rossby waves. The spatial and temporal information has also highlighted a particular situation in 1998 at 34N, with the simultaneous existence of two distinct wave components corresponding to wavelengths 500 km and 1000 km. Signatures of the waves in ocean color prompt the question of how Rossby waves influence surface chlorophyll concentrations. Several physical/biological processes have been suggested: the eddy pumping mechanism associated with nutrient injection, the uplifting of a deep chlorophyll maximum toward the surface, and the meridional advection of horizontal chlorophyll gradients by geostrophic currents associated with baroclinic Rossby waves. A statistical decomposition of the observed signal into the different processes modeled by Killworth et al. (2004) confirms a main contribution of the north-south advection of the surface chlorophyll-a gradients south of 28N. In this part of the basin, more than ∼ 70% of the signal is explained by this horizontal process. North of 28N, Rossby wave signatures seem to be due to the horizontal advection as well as the vertical nutrient injection (∼ 50% of the observed amplitude). This vertical mechanism may have an impact on the primary production in this part of the basin.

Published
2006

35. Coupled physical/biogeochemical modeling including O&lt;sub&gt;2&lt;/sub&gt;-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

Author

Gutknecht, E., primary, Dadou, I., additional, Le Vu, B., additional, Cambon, G., additional, Sudre, J., additional, Garçon, V., additional, Machu, E., additional, Rixen, T., additional, Kock, A., additional, Flohr, A., additional, Paulmier, A., additional, and Lavik, G., additional

Published
2012
Full Text
View/download PDF

43. Reconstruction of super-resolution ocean pCO2 and air-sea fluxes of CO2 from satellite imagery in the southeastern Atlantic.

Author

Hernández-Carrasco, I., Sudre, J., Garçon, V., Yahia, H., Garbe, C., Paulmier, A., Dewitte, B., Illig, S., Dadou, I., González-Dávila, M., and Santana-Casiano, J. M.

Subjects
CARBON dioxide in seawater, HIGH resolution imaging, REMOTE-sensing images, GREENHOUSE gases, OCEAN temperature measurement, OCEAN color measurement
Abstract

An accurate quantification of the role of the ocean as source/sink of greenhouse gases (GHGs) requires to access the high-resolution of the GHG air-sea flux at the interface. In this paper we present a novel method to reconstruct maps of surface ocean partial pressure of CO2 (pCO2) and air-sea CO2 fluxes at super resolution (4 km, i.e., 1/32° at these latitudes) using sea surface temperature (SST) and ocean color (OC) data at this resolution, and CarbonTracker CO2 fluxes data at low resolution (110 km). Inference of super-resolution pCO2 and air-sea CO2 fluxes is performed using novel nonlinear signal processing methodologies that prove efficient in the context of oceanography. The theoretical background comes from the microcanonical multi-fractal formalism which unlocks the geometrical determination of cascading properties of physical intensive variables. As a consequence, a multi-resolution analysis performed on the signal of the so-called singularity exponents allows for the correct and near optimal cross-scale inference of GHG fluxes, as the inference suits the geometric realization of the cascade. We apply such a methodology to the study offshore of the Benguela area. The inferred representation of oceanic partial pressure of CO2 improves and enhances the description provided by CarbonTracker, capturing the small-scale variability. We examine different combinations of ocean color and sea surface temperature products in order to increase the number of valid points and the quality of the inferred pCO2 field. The methodology is validated using in situ measurements by means of statistical errors. We find that mean absolute and relative errors in the inferred values of pCO2 with respect to in situ measurements are smaller than for CarbonTracker. [ABSTRACT FROM AUTHOR]

Published
2015
Full Text
View/download PDF

47. Coupled physical/biogeochemical modeling including O2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela.

Author

Gutknecht, E., Dadou, I., Le Vu, B., Cambon, G., Sudre, J., Garçon, V., Machu, E., Rixen, T., Kock, A., Flohr, A., Paulmier, A., and Lavik, G.

Subjects
BIOGEOCHEMISTRY, UPWELLING (Oceanography), MATHEMATICAL models, NITROGEN cycle, BIOLOGICAL productivity, CHEMICAL decomposition
Abstract

The Eastern Boundary Upwelling Systems (EBUS) contribute to one fifth of the global catches in the ocean. Often associated with Oxygen Minimum Zones (OMZs), EBUS represent key regions for the oceanic nitrogen (N) cycle. Important bioavailable N loss due to denitrification and anammox processes as well as greenhouse gas emissions (e.g, N2O) occur also in these EBUS. However, their dynamics are currently crudely represented in global models. In the climate change context, improving our capability to properly represent these areas is crucial, due to anticipated changes in the winds, productivity, and oxygen content. We developed a biogeochemical model (BioEBUS) taking into account the main processes linked with EBUS and associated OMZs. We implemented this model in a 3-D realistic coupled physical/biogeochemical configuration in the Namibian upwelling system (Northern Benguela) using the high-resolution hydrodynamical model ROMS. We present here a validation using in situ and satellite data as well as diagnostic metrics, and sensitivity analyses of key parameters and N2O parameterizations. The impact of parameter values on the OMZ off Namibia, on N loss, and on N2O concentrations and emissions is detailed. The model realistically reproduces the vertical distribution and seasonal cycle of observed oxygen, nitrate and Chl a concentrations, and the rates of microbial processes (e.g. NH+4 and NO-2 oxidation, NO-3 reduction and anammox) as well. Based on our sensitivity analyses, biogeochemical parameter values associated with organic matter decomposition, vertical sinking and nitrification play a key role for the low-oxygen water content, N loss and N2O concentrations in the OMZ. Moreover, the importance of both steps of nitrification, ammonium oxidation to nitrate with nitrite as an explicit intermediate, is highlighted to improve the representation of microbial activity linked with OMZ. The simulated minimum oxygen concentrations are driven by the poleward meridional advection of oxygen-depleted waters offshore of 300m isobath and by the biogeochemical activity inshore of this isobath, highlighting a spatial shift of dominant processes maintaining the minimum oxygen concentrations off Namibia. [ABSTRACT FROM AUTHOR]

Published
2012
Full Text
View/download PDF

49. Variability of the biological front south of Africa from Sea WiFS and a coupled physical-biological model.

Author

Llido, J., Machu, E., Sudre, J., Dadou, I., and Garçon, V.

Subjects
*OCEAN currents, *TIDAL currents, *BIOGEOCHEMISTRY, *ATMOSPHERIC pressure, *OCEANOGRAPHY
Abstract

The spatio-temporal variability of the biological front in the Agulhas Current system is investigated by comparing SeaWiFS chlorophyll a data and modeled chlorophyll fields over the October 1997-October 2001 period. The latter fields are simulated using a regional eddy-permitting (1/3° × 1/3°) coupled physical (AGAPE)-biological model forced by the monthly atmospheric NCEP/NCAR reanalysis. The annual cycle of the observed chlorophyll within the Agulhas Current system biogeochemical provinces is quite well reproduced by the model. The modeled phase of the seasonality in the SWSIG (South Western Subtropical Indian Gyre) is opposite to that of the SCZ (Subtropical Convergence Zone encompassing the Agulhas Front-AF, the Subtropical Front-STF and the Subantarctic Front-SAF), in agreement with observations. In the SWSIG, the switch from nitrates limitation to light control for the modeled phytoplankton growth shifts southward from winter to summer. In the SCZ, light availability modulates growth throughout the year. The wavelet average variance of the SeaWiFS data is slightly underestimated by the modeled chlorophyll variance over the four-year period within the 36–45S and 15–45E domain. This might originate in the interannual monthly NCEP forcing which does not include the high frequency information of the atmospheric fluxes. The model coarse resolution precludes a proper simulation of vertical motions produced by submesoscale flows thereby underestimating biological variability. Interestingly, the modeled chlorophyll distribution mimicks the strong early retroflection of the Agulhas Current in summer 2001 which induces a southward displacement of the STF/SAF double front. [ABSTRACT FROM AUTHOR]

Published
2004
Full Text
View/download PDF

50. Biomass Changes And Trophic Amplification Of Plankton In A Warmer Ocean

Author

Xabier Irigoien, Caleb Smith, Emanuela Clementi, Guillem Chust, Yuri Artioli, Eric Machu, Bettina A. Fach, Katerina Goubanova, Corinna Schrum, Jason Holt, Kostas Tsiaras, Marina Chifflet, Baris Salihoglu, Marco Zavatarelli, J. Icarus Allen, Dhanya Pushpadas, Briac Le Vu, Sarah Wakelin, Ute Daewel, Momme Butenschön, Laurent Bopp, George Petihakis, Véronique Garçon, Isabelle Dadou, Heather Cannaby, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), DYNBIO LEGOS, Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Echanges Côte-Large (ECOLA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Chust G., Allen J.I., Bopp L., Schrum C., Holt J., Tsiara K., Zavatarelli M., Chifflet M., Cannaby H., Dadou I., Daewel U., Wakelin S.L., Machu E., Pushpadas D., Butenschoen M., Artioli Y., Petihakis G., Smith C., Garcon V., Goubanova K., Le Vu B., Fach B. A., Salihoglu B., Clementi E., and Irigoien X.

Subjects
Food Chain, Climate Change, Oceans and Seas, Effects of global warming on oceans, sea warming, ecosystem model, Zooplankton, Phytoplankton, Animals, Environmental Chemistry, Biomass, 14. Life underwater, trophic amplification, Ecosystem, General Environmental Science, Trophic level, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Global and Planetary Change, Biomass (ecology), Ecology, food web, fungi, plankton, Temperature, Models, Theoretical, 15. Life on land, Food web, Sea surface temperature, Oceanography, 13. Climate action, foo web, Upwelling, Environmental science, trphic amplification, primary production
Abstract

1365-2486; Ocean warming can modify the ecophysiology and distribution of marine organisms, and relationships between species, with nonlinear interactions between ecosystem components potentially resulting in trophic amplification. Trophic amplification (or attenuation) describe the propagation of a hydroclimatic signal up the food web, causing magnification (or depression) of biomass values along one or more trophic pathways. We have employed 3-D coupled physical-biogeochemical models to explore ecosystem responses to climate change with a focus on trophic amplification. The response of phytoplankton and zooplankton to global climate-change projections, carried out with the IPSL Earth System Model by the end of the century, is analysed at global and regional basis, including European seas (NE Atlantic, Barents Sea, Baltic Sea, Black Sea, Bay of Biscay, Adriatic Sea, Aegean Sea) and the Eastern Boundary Upwelling System (Benguela). Results indicate that globally and in Atlantic Margin and North Sea, increased ocean stratification causes primary production and zooplankton biomass to decrease in response to a warming climate, whilst in the Barents, Baltic and Black Seas, primary production and zooplankton biomass increase. Projected warming characterised by an increase in sea surface temperature of 2.29 ± 0.05 ºC leads to a reduction in zooplankton and phytoplankton biomasses of 11% and 6%, respectively. This suggests negative amplification of climate driven modifications of trophic level biomass through bottom-up control, leading to a reduced capacity of oceans to regulate climate through the biological carbon pump. Simulations suggest negative amplification is the dominant response across 47% of the ocean surface and prevails in the tropical oceans; whilst positive trophic amplification prevails in the Arctic and Antarctic oceans. Trophic attenuation is projected in temperate seas. Uncertainties in ocean plankton projections, associated to the use of single global and regional models, imply the need for caution when extending these considerations into higher trophic levels. This article is protected by copyright. All rights reserved.

Published
2014
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results