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1. The Tropical Atlantic Observing System

Author

Foltz, GR, Brandt, P, Richter, I, Rodríguez-Fonseca, B, Hernandez, F, Dengler, M, Rodrigues, RR, Schmidt, JO, Yu, L, Lefevre, N, Da Cunha, L Cotrim, McPhaden, MJ, Araujo, M, Karstensen, J, Hahn, J, Martín-Rey, M, Patricola, CM, Poli, P, Zuidema, P, Hummels, R, Perez, RC, Hatje, V, Lübbecke, JF, Polo, I, Lumpkin, R, Bourlès, B, Asuquo, FE, Lehodey, P, Conchon, A, Chang, P, Dandin, P, Schmid, C, Sutton, A, Giordani, H, Xue, Y, Illig, S, Losada, T, Grodsky, SA, Gasparin, F, Lee, T, Mohino, E, Nobre, P, Wanninkhof, R, Keenlyside, N, Garcon, V, Sánchez-Gómez, E, Nnamchi, HC, Drévillon, M, Storto, A, Remy, E, Lazar, A, Speich, S, Goes, M, Dorrington, T, Johns, WE, Moum, JN, Robinson, C, Perruche, C, de Souza, RB, Gaye, AT, López-Parages, J, Monerie, P-A, Castellanos, P, Benson, NU, Hounkonnou, MN, Duhá, J Trotte, Laxenaire, R, and Reul, N

Subjects
Earth Sciences, Oceanography, Atmospheric Sciences, Life Below Water, Climate Action, tropical Atlantic Ocean, observing system, weather, climate, hurricanes, biogeochemistry, ecosystems, coupled model bias, Ecology, Geology
Abstract

The tropical Atlantic is home to multiple coupled climate variations covering a wide range of timescales and impacting societally relevant phenomena such as continental rainfall, Atlantic hurricane activity, oceanic biological productivity, and atmospheric circulation in the equatorial Pacific. The tropical Atlantic also connects the southern and northern branches of the Atlantic meridional overturning circulation and receives freshwater input from some of the world's largest rivers. To address these diverse, unique, and interconnected research challenges, a rich network of ocean observations has developed, building on the backbone of the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA). This network has evolved naturally over time and out of necessity in order to address the most important outstanding scientific questions and to improve predictions of tropical Atlantic severe weather and global climate variability and change. The tropical Atlantic observing system is motivated by goals to understand and better predict phenomena such as tropical Atlantic interannual to decadal variability and climate change; multidecadal variability and its links to the meridional overturning circulation; air-sea fluxes of CO2 and their implications for the fate of anthropogenic CO2; the Amazon River plume and its interactions with biogeochemistry, vertical mixing, and hurricanes; the highly productive eastern boundary and equatorial upwelling systems; and oceanic oxygen minimum zones, their impacts on biogeochemical cycles and marine ecosystems, and their feedbacks to climate. Past success of the tropical Atlantic observing system is the result of an international commitment to sustained observations and scientific cooperation, a willingness to evolve with changing research and monitoring needs, and a desire to share data openly with the scientific community and operational centers. The observing system must continue to evolve in order to meet an expanding set of research priorities and operational challenges. This paper discusses the tropical Atlantic observing system, including emerging scientific questions that demand sustained ocean observations, the potential for further integration of the observing system, and the requirements for sustaining and enhancing the tropical Atlantic observing system.

Published
2019

2. Surface mixing and biological activity in the four Eastern Boundary Upwelling Systems

Author

Rossi, V., Lopez, C., Hernandez-Garcia, E., Sudre, J., Garcon, V., and Morel, Y.

Subjects
Physics - Atmospheric and Oceanic Physics, Nonlinear Sciences - Chaotic Dynamics, Physics - Fluid Dynamics, Quantitative Biology - Populations and Evolution
Abstract

Eastern Boundary Upwelling Systems (EBUS) are characterized by a high productivity of plankton associated with large commercial fisheries, thus playing key biological and socio-economical roles. The aim of this work is to make a comparative study of these four upwelling systems focussing on their surface stirring, using the Finite Size Lyapunov Exponents (FSLEs), and their biological activity, based on satellite data. First, the spatial distribution of horizontal mixing is analysed from time averages and from probability density functions of FSLEs. Then we studied the temporal variability of surface stirring focussing on the annual and seasonal cycle. There is a global negative correlation between surface horizontal mixing and chlorophyll standing stocks over the four areas. To try to better understand this inverse relationship, we consider the vertical dimension by looking at the Ekman-transport and vertical velocities. We suggest the possibility of a changing response of the phytoplankton to sub/mesoscale turbulence, from a negative effect in the very productive coastal areas to a positive one in the open ocean., Comment: 12 pages. NPG Special Issue on "Nonlinear processes in oceanic and atmospheric flows". Open Access paper, available also at the publisher site: http://www.nonlin-processes-geophys.net/16/557/2009/

Published
2009
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3. Top marine predators track Lagrangian coherent structures

Author

Kai, E. Tew, Rossi, V., Sudre, J., Weimerskirch, H., Lopez, C., Hernandez-Garcia, E., Marsac, F., and Garcon, V.

Subjects
Quantitative Biology - Populations and Evolution, Nonlinear Sciences - Chaotic Dynamics, Physics - Atmospheric and Oceanic Physics
Abstract

Meso- and submesoscales (fronts, eddies, filaments) in surface ocean flow have a crucial influence on marine ecosystems. Their dynamics partly control the foraging behaviour and the displacement of marine top predators (tuna, birds, turtles, and cetaceans). In this work we focus on the role of submesoscale structures in the Mozambique Channel on the distribution of a marine predator, the Great Frigatebird. Using a newly developed dynamical concept, namely the Finite-Size Lyapunov Exponent (FSLE), we have identified Lagrangian coherent structures (LCSs) present in the surface flow in the Channel over a 2-month observation period (August and September 2003). By comparing seabirds' satellite positions with LCSs locations, we demonstrate that frigatebirds track precisely these structures in the Mozambique Channel, providing the first evidence that a top predator is able to track these FSLE ridges to locate food patches. After comparing bird positions during long and short trips, and different parts of these trips, we propose several hypotheses to understand how frigatebirds can follow these LCSs. The birds might use visual and/or olfactory cues and/or atmospheric current changes over the structures to move along these biological corridors. The birds being often associated to tuna schools around foraging areas, a thorough comprehension of their foraging behaviour and movement during the breeding season is crucial not only to seabirds' ecology but also to an appropriate ecosystemic approach of fisheries in the Channel.

Published
2009
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16. Phytoplankton distribution in the Agulhas system from a coupled physical-biological model

Author

Machu, E., Biastoch, A., Oschlies, A., Kawamiya, M., Lutjeharms, J.R.E., and Garcon, V.

Subjects
Detritus -- Analysis, Photosynthesis -- Analysis, Phytochemistry -- Analysis, Chlorophyll -- Analysis, Turbulence -- Analysis, Oceanography -- Analysis, Earth sciences
Abstract

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.dsr.2004.12.008 Byline: E. Machu (a), A. Biastoch (b), A. Oschlies (b), M. Kawamiya (b), J.R.E. Lutjeharms (c), V. Garcon (a) Abstract: The greater Agulhas Current system has several components with high mesoscale turbulence. The phytoplankton distribution in the southwest Indian Ocean reflects this activity. We have used a regional eddy-permitting, coupled physical-biological model to study the physical-biological interactions and to address the main processes responsible for phytoplankton distribution in three different biogeochemical provinces: the southwest Subtropical Indian Gyre (SWSIG), the subtropical convergence zone (SCZ) and the subantarctic waters (SAW) south of South Africa. The biological model with four compartments (Nitrate-Phytoplankton-Zooplankton-Detritus) adequately reproduces the observed field of chlorophyll a. The phase of the strong modelled seasonality in the SWSIG is opposite to that of the SCZ that forms the southern boundary of the subtropical gyre. Phytoplankton concentrations are governed by the source-minus-sink terms, which are one order of magnitude greater than the dynamical diffusion and advection terms. North of 35[degrees]S, in the SWSIG, phytoplankton growth is limited by nutrients supply throughout the year. However, deeper stratification, enhanced cross-frontal transport and higher detritus remineralization explain the simulated higher concentrations of phytoplankton found in winter in the SWSIG. The region between 35[degrees] and 40[degrees]S constitutes a transition zone between the SCZ and the oligotrophic subtropical province. Horizontal advection is the main process bringing nutrients for phytoplankton growth. The front at 34[degrees]S represents a dynamical barrier to an extension further to the north of this advection of nutrients. Within the SCZ, primary production is high during spring and summer. This high productivity depletes the nutrient standing stock built up during winter time. In winter, nutrients supply in the convergence zone is indeed large, but the deep mixing removes phytoplankton from the euphotic zone and inhibits photosynthesis, yielding lower surface chlorophyll a concentrations. Waters south of the Subantarctic Front have a summer biomass close to that of frontal waters and higher than for subtropical waters. However, these simulated concentrations are slightly higher than the observed ones suggesting that limitation by iron and/or silica may play a role. Author Affiliation: (a) Laboratoire d'Etudes en Geophysique et Oceanographie Spatiales, CNRS, UMR5566, 18, Avenue E. Belin, 31401 Toulouse cedex 9, France (b) Institut fur Meereskunde an der Universitat Kiel, Dusternbrooker Weg 20, 24105, Kiel, Germany (c) Department of Oceanography, University of Cape Town, 7700 Rondebosch, South Africa

Published
2005

17. Phytoplankton seasonal distribution from SeaWiFS data in the Agulhas Current system

Author

Machu, E. and Garcon, V.

Subjects
Indian Ocean -- Environmental aspects, Atlantic Ocean -- Environmental aspects, Marine phytoplankton -- Environmental aspects, Marine productivity -- Environmental aspects, Ocean currents -- Environmental aspects, Biological sciences, Earth sciences
Abstract

Research on the Agulhas Current, located between the Indian and Atlantic Oceans, indicates that seasonal and spatial variation in chlorophyll distribution can be attributed to changes in the strength of subtropical gyre and cross-frontal mixing, changes in density of the juxtaposed fronts, and changes in light availability and mixed-layer depth.

Published
2001

18. Transports of the Brazil and Malvinas currents at their confluence

Author

Maamaatuaiahutapu, K., Garcon, V., Provost, C., and Mercier, H.

Subjects
South Atlantic Ocean -- Research, Falkland Islands -- Research, Brazil -- Research, Ocean currents -- Research, Biological sciences, Earth sciences
Abstract

The geographic transports of the currents at the confluence Brazil/Malvinas between 35S and 42S over the continental slop were measured. This research employed a new CTD dataset for the development of a nonlinear inverse model and the measurement of geostrophic transports. A total transport of 45 +- 7 Sv was derived from two inversions implemented at two different levels of no motion. Discrepancies between the two inversions were found at the Brazil Current region. Total transport at one case was 30 +- 7 Sv while total transport at the other was 56 +- 8 Sv.

Published
1998

19. 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

20. Seasonal variability of the southern tip of the oxygen minimum zone in the Eastern South Pacific (30 degrees - 38 degrees S) : a modeling study

Author

Pizarro-Koch, M., Pizarro, O., Dewitte, Boris, Montes, I., Ramos, M., Paulmier, Aurélien, and Garcon, V.

Subjects
Oxygen minimum zone, Oxygen budget, Eddy fluxes, Peru-Chile Undercurrent, Eastern South Pacific
Abstract

We investigate the seasonal variability of the southern tip (30 degrees-38 degrees S) of the eastern South Pacific oxygen minimum zone (OMZ) based on a high horizontal resolution (1/12 degrees) regional coupled physical-biogeochemical model simulation. The simulation is validated by available in situ observations and the OMZ seasonal variability is documented. The model OMZ, bounded by the contour of 45 mu M, occupies a large volume (4.5x10(4) km(3)) during the beginning of austral winter and a minimum (3.5x10(4) km(3)) at the end of spring, just 1 and 2 months after the southward transport of the Peru-Chile Undercurrent (PCUC) is maximum and minimum, respectively. We showed that the PCUC significantly impacts the alongshore advection of dissolved oxygen (DO) modulating the OMZ seasonal variability. However, zonal transport of DO by meridionally alternating zonal jets and mesoscale eddy fluxes play also a major role in the seasonal and spatial variability of the OMZ. Consistently, a DO budget analysis reveals a significant contribution of advection terms to the rate of change of DO and the prominence of mesoscale variability within the seasonal cycle of these terms. Biogeochemical processes and horizontal and vertical mixing, associated with subgrid scale processes, play only a secondary role in the OMZ seasonal cycle. Overall, our study illustrates the interplay of mean and (mesoscale) eddy-induced transports of DO in shaping the OMZ and its seasonal cycle off Central Chile.

Published
2019

21. 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

22. The Tropical Atlantic Observing System

Author

Foltz, G. R., Brandt, P., Richter, I., Rodríguez-fonseca, B., Hernandez, F., Dengler, M., Rodrigues, R. R., Schmidt, J. O., Yu, L., Lefevre, N., Da Cunha, L. Cotrim, Mcphaden, M. J., Araujo, M., Karstensen, J., Hahn, J., Martín-rey, M., Patricola, C. M., Poli, P., Zuidema, P., Hummels, R., Perez, Rc, Hatje, V., Lübbecke, J. F., Polo, I., Lumpkin, R., Bourlès, Bernard, Asuquo, F. E., Lehodey, P., Conchon, A., Chang, P., Dandin, P., Schmid, C., Sutton, A., Giordani, H., Xue, Y., Illig, S., Losada, T., Grodsky, S. A., Gasparin, F., Lee, T., Mohino, E., Nobre, P., Wanninkhof, R., Keenlyside, N., Garcon, V., Sánchez-gómez, E., Nnamchi, H. C., Drévillon, M., Storto, A., Remy, E., Lazar, A., Speich, S., Goes, M., Dorrington, T., Johns, W. E., Moum, J. N., Robinson, C., Perruche, Coralie, De Souza, R. B., Gaye, A. T., López-parages, J., Monerie, P.-a., Castellanos, P., Benson, N. U., Hounkonnou, M. N., Duhá, J. Trotte, Laxenaire, R., Reul, Nicolas, Foltz, G. R., Brandt, P., Richter, I., Rodríguez-fonseca, B., Hernandez, F., Dengler, M., Rodrigues, R. R., Schmidt, J. O., Yu, L., Lefevre, N., Da Cunha, L. Cotrim, Mcphaden, M. J., Araujo, M., Karstensen, J., Hahn, J., Martín-rey, M., Patricola, C. M., Poli, P., Zuidema, P., Hummels, R., Perez, Rc, Hatje, V., Lübbecke, J. F., Polo, I., Lumpkin, R., Bourlès, Bernard, Asuquo, F. E., Lehodey, P., Conchon, A., Chang, P., Dandin, P., Schmid, C., Sutton, A., Giordani, H., Xue, Y., Illig, S., Losada, T., Grodsky, S. A., Gasparin, F., Lee, T., Mohino, E., Nobre, P., Wanninkhof, R., Keenlyside, N., Garcon, V., Sánchez-gómez, E., Nnamchi, H. C., Drévillon, M., Storto, A., Remy, E., Lazar, A., Speich, S., Goes, M., Dorrington, T., Johns, W. E., Moum, J. N., Robinson, C., Perruche, Coralie, De Souza, R. B., Gaye, A. T., López-parages, J., Monerie, P.-a., Castellanos, P., Benson, N. U., Hounkonnou, M. N., Duhá, J. Trotte, Laxenaire, R., and Reul, Nicolas

Abstract

The tropical Atlantic is home to multiple coupled climate variations covering a wide range of timescales and impacting societally relevant phenomena such as continental rainfall, Atlantic hurricane activity, oceanic biological productivity, and atmospheric circulation in the equatorial Pacific. The tropical Atlantic also connects the southern and northern branches of the Atlantic meridional overturning circulation and receives freshwater input from some of the world’s largest rivers. To address these diverse, unique, and interconnected research challenges, a rich network of ocean observations has developed, building on the backbone of the Prediction and Research Moored Array in the Tropical Atlantic (PIRATA). This network has evolved naturally over time and out of necessity in order to address the most important outstanding scientific questions and to improve predictions of tropical Atlantic severe weather and global climate variability and change. The tropical Atlantic observing system is motivated by goals to understand and better predict phenomena such as tropical Atlantic interannual to decadal variability and climate change; multidecadal variability and its links to the meridional overturning circulation; air-sea fluxes of CO2 and their implications for the fate of anthropogenic CO2; the Amazon River plume and its interactions with biogeochemistry, vertical mixing, and hurricanes; the highly productive eastern boundary and equatorial upwelling systems; and oceanic oxygen minimum zones, their impacts on biogeochemical cycles and marine ecosystems, and their feedbacks to climate. Past success of the tropical Atlantic observing system is the result of an international commitment to sustained observations and scientific cooperation, a willingness to evolve with changing research and monitoring needs, and a desire to share data openly with the scientific community and operational centers. The observing system must continue to evolve in order to meet an expanding set

Published
2019
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23. Oxygen

Author

Cochran, J. Kirk, Bokuniewicz, Henry, Yager, Patricia, Garcon, V., Gregoire, M., Isensee, K., Karstensen, Johannes, Cochran, J. Kirk, Bokuniewicz, Henry, Yager, Patricia, Garcon, V., Gregoire, M., Isensee, K., and Karstensen, Johannes

Published
2019

26. 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

27. 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

28. Small-scale features of temperature and salinity surface fields in the Coral Sea

Author

Maes, C., Dewitte, B., Sudre, J., Garcon, V., Varillon, D., 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 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
TEMPERATURE DE SURFACE, MESURE IN SITU, MECHANISM, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, SALINITE, SSS, PACIFIC WARM POOL, SST, VARIABILITY, VARIATION TEMPORELLE, in situ observations, OCEAN, EASTERN EDGE, EL-NINO, ONSET, INTERACTION OCEAN ATMOSPHERE, BARRIER LAYER, NETWORK, Coral Sea, TROPICAL PACIFIC, DISTRIBUTION SPATIALE, ANALYSE STATISTIQUE
Abstract

ISI Document Delivery No.: 257JQ Times Cited: 0 Cited Reference Count: 51 Cited References: Alory G, 2012, J GEOPHYS RES-OCEANS, V117, DOI 10.1029/2011JC007802 Barton IJ, 2007, J ATMOS OCEAN TECH, V24, P1773, DOI 10.1175/JTECH2084.1 Benhamou S., 2011, PLOS ONE, V6 Bingham FM, 2002, J GEOPHYS RES-OCEANS, V107, DOI [10.1029/2000JC000767, 10.1029/2000jc000767] Boyer TP, 2002, J GEOPHYS RES-OCEANS, V107, DOI 10.1029/2001JC000829 Chen J, 2012, J OCEANOGR, V68, P687, DOI 10.1007/s10872-012-0126-8 Choukroun S, 2010, J GEOPHYS RES-OCEANS, V115, DOI 10.1029/2009JC005761 Delcroix T, 2005, DEEP-SEA RES PT I, V52, P787, DOI 10.1016/j.dsr.2004.11.012 Delcroix T, 2011, DEEP-SEA RES PT I, V58, P38, DOI 10.1016/j.dsr.2010.11.002 Dewitte B, 2011, J GEOPHYS RES-OCEANS, V116, DOI 10.1029/2010JC006495 DONGUY JR, 1994, PROG OCEANOGR, V34, P45, DOI 10.1016/0079-6611(94)90026-4 Fisher M., 2004, GEOPHYS RES LETT, V31, DOI 10.1029/2004GL020112 Freeman LA, 2012, J GEOPHYS RES-OCEANS, V117, DOI 10.1029/2011JC007099 Gasparin F, 2011, DEEP-SEA RES PT I, V58, P956, DOI 10.1016/j.dsr.2011.05.007 Gorman MK, 2012, PALEOCEANOGRAPHY, V27, DOI 10.1029/2012PA002302 Hendon H, 2005, S-P B ENVIRON SCI, P223, DOI 10.1007/3-540-27250-X_7 Henin C, 1996, DEEP-SEA RES PT I, V43, P1833, DOI 10.1016/S0967-0637(96)00084-2 Henocq C, 2010, J ATMOS OCEAN TECH, V27, P192, DOI 10.1175/2009JTECHO670.1 Hernandez-Carrasco I., 2012, J GEOPHYS RES, V117, DOI 10.1029/2012JC008222 Hernandez-Carrasco I, 2011, OCEAN MODEL, V36, P208, DOI 10.1016/j.ocemod.2010.12.006 Huffman GJ, 2007, J HYDROMETEOROL, V8, P38, DOI 10.1175/JHM560.1 Ioualalen M, 2003, J OCEANOGR, V59, P105, DOI 10.1023/A:1022876708829 Kawamura R, 2002, J GEOPHYS RES-ATMOS, V107, DOI 10.1029/2001JD001070 Klemas V, 2011, J COASTAL RES, V27, P830, DOI 10.2112/JCOASTRES-D-11-00060.1 Leuliette EW, 1999, J PHYS OCEANOGR, V29, P599, DOI 10.1175/1520-0485(1999)0292.0.CO;2 Lin JWB, 2000, J ATMOS SCI, V57, P2793, DOI 10.1175/1520-0469(2000)0572.0.CO;2 MADDEN RA, 1972, J ATMOS SCI, V29, P1109, DOI 10.1175/1520-0469(1972)0292.0.CO;2 Maes C, 2004, GEOPHYS RES LETT, V31, DOI 10.1029/2004GL019867 Maes C, 2010, SOLA, V6, P129, DOI 10.2151/sola.2010-033 Maes C, 2002, GEOPHYS RES LETT, V29, DOI 10.1029/2002GL016029 Maes C, 2005, J CLIMATE, V18, P104, DOI 10.1175/JCLI-3214.1 Picaut J, 1996, SCIENCE, V274, P1486, DOI 10.1126/science.274.5292.1486 Pierce DW, 2012, GEOPHYS RES LETT, V39, DOI 10.1029/2012GL053389 Qiu B, 2009, J PHYS OCEANOGR, V39, P404, DOI 10.1175/2008JPO3988.1 Reul N., 2012, SMOS LEVEL 3 SSS RES, P21 Reul N., 2013, SURV GEOPHYS, P1, DOI 10.1007/GEOP-D-13-00003 Reverdin G, 2012, J GEOPHYS RES-OCEANS, V117, DOI 10.1029/2011JC007549 Reynolds RW, 2007, J CLIMATE, V20, P5473, DOI 10.1175/2007JCLI1824.1 Ridgway KR, 2003, PROG OCEANOGR, V56, P189, DOI 10.1016/S0079-6611(03)00004-1 Roemmich D, 1998, J GEOPHYS RES-OCEANS, V103, P13041, DOI 10.1029/98JC00583 Roemmich D, 2009, OCEANOGRAPHY, V22, P46 Rossi V, 2008, GEOPHYS RES LETT, V35, DOI 10.1029/2008GL033610 SCHMITT RW, 1995, REV GEOPHYS, V33, P1395, DOI 10.1029/95RG00184 Sudre J., 2013, LIMNOL OCEANOGR FLUI, V3, P1, DOI 10.1215/21573689-2071927 Takahashi K, 2011, GEOPHYS RES LETT, V38, DOI 10.1029/2011GL047364 Toole J. M., 2001, INT GEOPHYS SERIES, V77, P337 Torrence C, 1998, B AM METEOROL SOC, V79, P61, DOI 10.1175/1520-0477(1998)0792.0.CO;2 Wachenfeld D., 2007, CLIMATE CHANGE GREAT Waugh DW, 2006, J PHYS OCEANOGR, V36, P526, DOI 10.1175/JPO2865.1 Wheeler MC, 2004, MON WEATHER REV, V132, P1917, DOI 10.1175/1520-0493(2004)1322.0.CO;2 Yueh S., 2012, IEEE INT GEOSC REM S Maes, Christophe Dewitte, Boris Sudre, Joel Garcon, Veronique Varillon, David Institut de Recherche pour le Developpement (IRD); Centre National de la Recherche Scientifique (CNRS) Sea surface salinity data derived from thermosalinograph instruments installed onboard voluntary observing ships are freely distributed by the French Sea Surface Salinity Observation Service (http://www.legos.obs-mip.fr/observations/sss/). The TRMM data were acquired as part of the activities of NASA's Science Mission Directorate, and are archived and distributed by the Goddard Earth Sciences (GES) Data and Information Services Center (DISC). Special thanks go to Cristobal Lopez and Emilio Hernandez-Garcia for providing their code for the FSLE computation, and to Serena Illig for her help on the wavelet analysis. Comments on the original version from Dave Behringer were greatly appreciated, and we would like also to gratefully thank Tangdong Qu and the other anonymous reviewer for their fruitful comments. This work is supported by the Institut de Recherche pour le Developpement (IRD) and by the Centre National de la Recherche Scientifique (CNRS). 0 AMER GEOPHYSICAL UNION WASHINGTON J GEOPHYS RES-OCEANS; The small-scale features in sea surface temperature and salinity fields (SST and SSS) of the Coral Sea are examined using high horizontal spatial and short-term temporal in situ measurements. These features are extracted from thermosalinographs (TSGs) gathered onboard commercial and research vessels and at one long-term fixed station. The analyses are performed along the vessel tracks and the structures of small-scale features are extracted by high-pass spatial filtering the original TSG data. For SSS, it is shown that the features at the scale of mesoscale eddies (approximate to 100 km) vary from about -1.1 to +0.6 psu in the Coral Sea region. Processes sustaining such range include rainfall events, stirring by mesoscale eddies, and the latitudinal displacement of the sharp front associated with the edge of the Western Pacific Warm Pool at the seasonal time scales. The TSG data have revealed the presence of a sharp front (0.4-0.6 psu) between the subtropical and equatorial waters instead of a smooth gradient in the standard SSS climatologies. Within the context of recent remotely sensed observations of salinity, this could represent an important limitation for the validation and calibration of satellite products. In addition to these spatial considerations, temporal variations at one long-term station near Vanuatu show that the coupled air-sea responses to intraseasonal tropical variability, such as the Madden-Julian Oscillation, may have a signature in both SST and SSS fields. However, this response is found to be complex and not necessarily in phase. In the Coral Sea region, our results suggest that MJO-induced variability on SST and SSS exhibit little coherency at the seasonal time scales.

Published
2013
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29. Coupled physical/biogeochemical modeling including O-2-dependent processes in the Eastern Boundary Upwelling Systems: application in the Benguela

Author

Gutknecht, E., Dadou, Isabelle, Le Vu, B., Cambon, Gildas, Sudre, J., Garcon, V., Machu, Eric, Rixen, T., Kock, A., Flohr, A., Paulmier, A., Lavik, G., 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), Laboratoire de physique des océans (LPO), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Leibniz Centre for Tropical Marine Research (ZMT), Forschungsbereich Marine Biogeochemie IFM-GEOMAR, Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR), Instituto del Mar del Peru (IMARPE), Max Planck Institute for Marine Microbiology, Max-Planck-Gesellschaft, Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), and 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)

Subjects
SALINITE, BIOLOGICAL productivity, COUCHE MINIMUM D'OXYGENE, lcsh:QE1-996.5, lcsh:Life, MATHEMATICAL models, UPWELLING, SEL NUTRITIF, BIOGEOCHEMISTRY, CHLOROPHYLLE, CYCLE BIOGEOCHIMIQUE, MODELE, lcsh:Geology, lcsh:QH501-531, DECOMPOSITION (Chemistry), lcsh:QH540-549.5, NITROGEN cycle, lcsh:Ecology, TEMPERATURE, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, UPWELLING (Oceanography)
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 the poleward meridional advection of oxygen-depleted waters offshore of a 300 m isobath and by the biogeochemical activity inshore of this isobath, highlighting a spatial shift of dominant processes maintaining the minimum oxygen concentrations off Namibia. In the OMZ off Namibia, the magnitude of N2O outgassing and of N loss is comparable. Anammox contributes to about 20% of total N loss, an estimate lower than currently assumed (up to 50%) for the global ocean.

Published
2013
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30. Electrochemical Behaviour Of Isopoly- And Heteropolyoxomolybdates Formed During Anodic Oxidation Of Molybdenum In Seawater

Author

Jońca, Justyna, Barus, C., Giraud, W., Thouron, D., Garcon, V., Comtat, M., 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), and 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)

Subjects
heteropolyoxomolybdates, MEDIA, voltammetry, IDENTIFICATION, ELECTROLYTES, DISSOLUTION, SILICATE, molybdenum oxidation, PHOSPHATE, isopolyoxomolybdates, WATER, TRANSPASSIVITY, AMPEROMETRIC DETECTION
Abstract

ISI Document Delivery No.: 995BG Times Cited: 1 Cited Reference Count: 29 Cited References: Armstrong R. D., 1977, J ELECTROANAL CHEM, V84, P62 Bard A.J., 2001, ELECTROCHEMICAL METH, P341 Bojinov M, 1996, ELECTROCHIM ACTA, V41, P1173, DOI 10.1016/0013-4686(95)00468-8 BOJINOV M, 1995, J ELECTROANAL CHEM, V381, P123, DOI 10.1016/0022-0728(94)03675-S Carpenter NG, 1997, ELECTROANAL, V9, P1311, DOI 10.1002/elan.1140091703 CHALILPOYIL P, 1978, INORG CHEM, V17, P2418, DOI 10.1021/ic50187a017 Chukalovskaya T. V., 1984, ZASHCH MET, V20, P864 Cruywagen JJ, 2002, INORG CHIM ACTA, V331, P322, DOI 10.1016/S0020-1693(02)00700-4 Easterly CE, 2001, APPL SPECTROSC, V55, P1671, DOI 10.1366/0003702011953991 FOGG AG, 1981, ANALYST, V106, P1288, DOI 10.1039/an9810601288 Gordon L.I., 1993, WOCE METHOD MANUAL, P68 Guanghan L, 1999, Talanta, V49, P511, DOI 10.1016/S0039-9140(99)00038-7 HARDEN SM, 1984, ANAL CHEM, V56, P2218, DOI 10.1021/ac00276a053 Himeno S, 1997, B CHEM SOC JPN, V70, P631, DOI 10.1246/bcsj.70.631 HULL MN, 1972, J ELECTROANAL CHEM, V38, P143, DOI 10.1016/0368-1874(72)80177-1 Itagaki M, 1997, ELECTROCHIM ACTA, V42, P1081, DOI 10.1016/S0013-4686(96)00253-8 Jonca J, 2011, TALANTA, V87, P161, DOI 10.1016/j.talanta.2011.09.056 Koening M., 1963, BER BUNSEN PHYS CHEM, V67, P837 Krishnan CV, 2007, INT J ELECTROCHEM SC, V2, P29 Kuzenstov V. V., 2004, RUSS J ELECTROCHEM+, V40, P711 Lacombe M, 2007, MAR CHEM, V106, P489, DOI 10.1016/j.marchem.2007.05.002 Lacombe M, 2008, TALANTA, V77, P744, DOI 10.1016/j.talanta.2008.07.023 Pettersson AK, 1999, ANAL CHIM ACTA, V378, P183, DOI 10.1016/S0003-2670(98)00637-0 Pope M. T., 1983, HETEROPOLY ISOPOLY O Quintana JC, 2004, TALANTA, V63, P567, DOI 10.1016/j.talanta.2003.11.040 Thouron D, 2003, ANAL CHEM, V75, P2601, DOI 10.1021/ac020696+ Truesdale W. V., 1976, ANALYST, V101, P19 TYTKO KH, 1973, ANGEW CHEM INT EDIT, V12, P330, DOI 10.1002/anie.197303301 Wang K, 1998, ELECTROCHIM ACTA, V43, P2459 Jonca, Justyna Barus, Carole Giraud, William Thouron, Daniele Garcon, Veronique Comtat, Maurice Marie Curie PhD grant within SENSEnet ITN (EC Framework Programme 7) [237868]; Foundation STAE (Sciences and Technologies for Space and Aeronautics) within the project "MAISOE'' (Microlaboratories of in situ Analyses for Environmental Observatories) We are grateful to the GET (Geoscience Environment Toulouse) laboratory (Toulouse, France) for access to a spectrophotometer. Justyna Jonca is supported by a Marie Curie PhD grant within SENSEnet ITN (EC Framework Programme 7, grant agreement No 237868). William Giraud is supported by the Foundation STAE (Sciences and Technologies for Space and Aeronautics) within the project "MAISOE'' (Microlaboratories of in situ Analyses for Environmental Observatories). 1 ELECTROCHEMICAL SCIENCE GROUP BELGRADE INT J ELECTROCHEM SC; The electrochemical behaviour of isopoly- and heteropolyoxomolybdates formed during anodic oxidation of molybdenum in seawater at constant current intensity was investigated in this work. The results supported by spectrophotometry clearly indicate the formation of mixed valence molybdates (V/VI) during this process. The electrochemical behaviour of isopolyoxomolybdates shows a typical quasi-reversible mass-transport limited system coupled with an adsorption of reduced species and under some kinetic limitations. For heteropolyoxomolybdates a reversible mass-transport limited system coupled with an homogeneous chemical reaction was found. The coupled reaction, probably protonation, prevents a rapid heterogeneous electron transfer for heteropolyoxomolybdate complex. The phenomenon is more noticeable for the phosphomolybdate complex since the protonation step has a greater influence on the registered voltammograms. The presented results have a great importance in research areas where molybdate chemistry is used in detection of silicate and phosphate, namely in seawater.

Published
2012

31. CO2 maximum in the oxygen minimum zone (OMZ)

Author

Paulmier, Aurélien, Ruiz-Pino, D., Garcon, V., 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), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Muséum national d'Histoire naturelle (MNHN)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-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 Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-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), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-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 Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL)

Subjects
lcsh:Geology, lcsh:QH501-531, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], lcsh:QH540-549.5, lcsh:QE1-996.5, lcsh:Life, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], lcsh:Ecology
Abstract

International audience; Oxygen minimum zones (OMZs), known as suboxic layers which are mainly localized in the Eastern Boundary Upwelling Systems, have been expanding since the 20th "high CO2" century, probably due to global warming. OMZs are also known to significantly contribute to the oceanic production of N2O, a greenhouse gas (GHG) more efficient than CO2. However, the contribution of the OMZs on the oceanic sources and sinks budget of CO2, the main GHG, still remains to be established. We present here the dissolved inorganic carbon (DIC) structure, associated locally with the Chilean OMZ and globally with the main most intense OMZs (O2-1) in the open ocean. To achieve this, we examine simultaneous DIC and O2 data collected off Chile during 4 cruises (2000-2002) and a monthly monitoring (2000-2001) in one of the shallowest OMZs, along with international DIC and O2 databases and climatology for other OMZs. High DIC concentrations (>2225 μmol kg-1, up to 2350 μmol kg-1) have been reported over the whole OMZ thickness, allowing the definition for all studied OMZs a Carbon Maximum Zone (CMZ). Locally off Chile, the shallow cores of the OMZ and CMZ are spatially and temporally collocated at 21° S, 30° S and 36° S despite different cross-shore, long-shore and seasonal configurations. Globally, the mean state of the main OMZs also corresponds to the largest carbon reserves of the ocean in subsurface waters. The CMZs-OMZs could then induce a positive feedback for the atmosphere during upwelling activity, as potential direct local sources of CO2. The CMZ paradoxically presents a slight "carbon deficit" in its core (~10%), meaning a DIC increase from the oxygenated ocean to the OMZ lower than the corresponding O2 decrease (assuming classical C/O molar ratios). This "carbon deficit" would be related to regional thermal mechanisms affecting faster O2 than DIC (due to the carbonate buffer effect) and occurring upstream in warm waters (e.g., in the Equatorial Divergence), where the CMZ-OMZ core originates. The "carbon deficit" in the CMZ core would be mainly compensated locally at the oxycline, by a "carbon excess" induced by a specific remineralization. Indeed, a possible co-existence of bacterial heterotrophic and autotrophic processes usually occurring at different depths could stimulate an intense aerobic-anaerobic remineralization, inducing the deviation of C/O molar ratios from the canonical Redfield ratios. Further studies to confirm these results for all OMZs are required to understand the OMZ effects on both climatic feedback mechanisms and marine ecosystem perturbations.

Published
2011
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32. Determination of geostrophic vector field on high resolution SST images from the energy cascade

Author

Yahia, H., Sudre, J., Pottier, C., Garcon, V., 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), 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), 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), 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)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
[INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2009

33. 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
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34. Nitrogen transfers off Walvis Bay: a 3-D coupled physical/biogeochemical modeling approach in the Namibian upwelling system

Author

Gutknecht, E., Dadou, Isabelle, Marchesiello, P., Cambon, Gildas, Le Vu, B., Sudre, J., Garcon, V., Machu, Eric, Rixen, T., Kock, A., Flohr, A., Paulmier, A., Lavik, G., Gutknecht, E., Dadou, Isabelle, Marchesiello, P., Cambon, Gildas, Le Vu, B., Sudre, J., Garcon, V., Machu, Eric, 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 degrees S and 24 degrees 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 (O-2 < 25 mmol O-2 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+/-3.9x10(10) mol N yr(-1) at 10 degrees 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%

Published
2013
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36. 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
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37. An eddy-permitting coupled physical-biological model of the North Atlantic. Part II: Ecosystem dynamics and comparison with satellite and JGOFS local studies data

Author

Oschlies, Andreas, Koeve, Wolfgang, and Garcon, V.

Abstract

A model of biological production in the euphotic zone of the North Atlantic has been developed by coupling a Nitrate, Phytoplankton, Zooplankton, Detritus (NPZD) nitrogen-based ecosystem model with an eddy-permitting circulation model. The upper ocean physical and biological results are presented for an experiment with monthly climatological forcing. A comparison with satellite ocean color data shows that the model is capable of a realistic description of the main seasonal and regional patterns of surface chlorophyll. Agreement is also good for primary production except in the subtropical gyre where the model produces values more than an order of magnitude smaller than derived from satellite observations. In situ data available at Joint Global Ocean Flux Study (JGOFS) time series and local study sites (Bermuda Atlantic Time-series Study (BATS), 32°N, 65°W; North Atlantic Bloom Experiment (NABE), 47°N, 2O°W; EUMELI oligotrophic, 21°N, 31°W) are used for a more detailed analysis of the model's capability to simultaneously reproduce seasonal ecosystem dynamics in different biological provinces of the North Atlantic Ocean. The seasonal cycle of phytoplankton biomass and nitrate is simulated quite realistically at all sites. Main discrepancies between model and observations are a large zooplankton peak, required by the model to end the phytoplankton spring bloom at the 47°N, 20°W site, and the underestimation of primary production at EUMELI and under oligotrophic summer conditions at BATS. The former model deficiency can be related to the neglect of phytoplankton aggregation; the latter is caused by too inefficient recycling of nutrients within the euphotic zone. Model improvements are suggested for further steps toward a realistic basin-wide multiprovinces simulation with a single ecosystem model.

Published
2000

38. Short-term photoacclimation effects on photoinhibition of phytoplankton in the Drake Passage (Southern Ocean)

Author

Alderkamp, A.C., Garcon, V., de Baar, H.J.W., Arrigo, K.R., Alderkamp, A.C., Garcon, V., de Baar, H.J.W., and Arrigo, K.R.

Abstract

We assessed whether short-term photoacclimation responses of natural phytoplankton populations in the Drake Passage (Southern Ocean) were affecting protection from photodamage as cells are mixed up to the surface from depth. To this end, we measured phytoplankton fluorescence characteristics and their ratio of xanthophyll cycle pigment to photosynthetic pigments within the upper mixed layer (UML) and in short-term deck incubation experiments. Phytoplankton within the UML photoacclimated by increasing their ratio of xanthophyll cycle (diadinoxanthin [dd] and diatoxanthin [dt]) pigments to chlorophyll a. The photoacclimation processes observed within the UML did, however, not influence the protection of phytoplankton from photodamage during short-term near-surface irradiance experiments. Exposure to near-surface irradiance resulted in photodamage in all experiments, regardless of the phytoplankton community composition and irradiance levels. Incubating phytoplankton for six hours at either 2% or 50% of surface irradiance prior to exposure to near-surface irradiance did not alter the photodamage characteristics. This suggests that short-term photoacclimation processes within the UML are not adequate to protect phytoplankton from photodamage when cells are mixed up to the surface from depth, and that repair of damaged photosystems is crucial for maintaining photosynthesis under fluctuating irradiance conditions, even at very low mean irradiance levels. Likely, continuously operating photoacclimation processes offset to some extent the negative effects of photodamage on photosynthetic performance, albeit with increased metabolic costs.

Published
2011

40. An eddy permitting coupled physical-biological model of the North Atlantic. Part I: Sensitivity to advection numerics and mixed layer physics

Author

Oschlies, Andreas and Garcon, V.

Subjects
Physics::Atmospheric and Oceanic Physics
Abstract

Physical influences on biological primary production in the North Atlantic are investigated by coupling a four-component pelagic ecosystem model with a high-resolution numerical circulation model. A series of sensitivity experiments demonstrates the important role of an accurate formulation of upper ocean turbulence and advection numerics. The unrealistically large diffusivity implicit in upstream advection approximately doubles primary production when compared with a less diffusive, higher-order, positive-definite advection scheme.This is of particular concern in the equatorial upwelling region where upstream advection leads to a considerable increase of upper ocean nitrate concentrations. Counteracting this effect of unrealistically large implicit diffusion by changes in the biological model could easily lead to misconceptions in the interpretation of ecosystem dynamics. Subgrid-scale diapycnal diffusion strongly controls biological production in the subtropical gyre where winter mixing does not reach the nutricline. The parameterization of vertical viscosity is important mainly in the equatorial region where friction becomes an important agent in the momentum balance.

Published
1999

41. 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

42. 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

43. 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

46. Merging SeaWiFS and MODIS/Aqua Ocean Color Data in North and Equatorial Atlantic Using Weighted Averaging and Objective Analysis

Author

Pottier, C, Garcon, V, Larnicol, G, Sudre, J, Schaeffer, P, Le Traon, Pierre-yves, Pottier, C, Garcon, V, Larnicol, G, Sudre, J, Schaeffer, P, and Le Traon, Pierre-yves

Abstract

Two approaches of ocean color data merging were tested and compared in the North and Equatorial Atlantic Basin: the weighted averaging and the objective analysis. The datasets used were the daily level-3 binned data of chlorophyll-a from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and Moderate Resolution Imaging Spectroradiometer on the Aqua satellite over the year 2003, which is the first common full year of operation. Since they represent input for both approaches, matchups between the satellite and the in situ data from the SeaWiFS Bio-optical Archive and Storage System and the Atlantic Meridional Transect were first studied to compute a spatial map of the root mean-square error and of the bias. Because of the log distribution of the chlorophyll fields, each approach was applied to untransformed and log-transformed values. The application of the weighted averaging to log-transformed values does not show significant differences in comparison to its application to untransformed values. This is not the case, however, for the objective analysis that gives better results when applied to logtransformed values. Both approaches give combined chlorophyll data of equivalent quality, although the objective analysis could be improved with a better statistical characterization of noise and signal covariance. The main advantage of the objective analysis is its ability to interpolate in space (and time) by taking into account the characteristic scales of chlorophyll-a. As a result, the spatial coverage of the combined data is at least twice as large in the case of objective analysis than weighted averaging. OCR NOT CONTROLLED

Published
2006
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47. 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

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