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81 results on '"Alexis Chaigneau"'

1. Tidal Impacts on Zooplankton Dynamics in a Major Ocean-Lagoon Channel: Insights from a 25-Hour Intensive Survey in the Cotonou Channel, Benin

Author: Hervé Hotèkpo Akodogbo, Fridolin Ubald Dossou-Sognon, François Talomonwo Ouinsou, Thalasse Tchémangnihodé Avocegan, Junior Patric Kouglo, Olaègbè Victor Okpeitcha, Arnaud Assogba, Zacharie Sohou, Yves Morel, and Alexis Chaigneau
Subjects: zooplankton, tidal cycle, cotonou channel, rotifers, copepods, Synchaeta bicornis, Naval architecture. Shipbuilding. Marine engineering, VM1-989, Oceanography, GC1-1581
Abstract: This study investigates the effects of tidal cycles on the zooplankton community within the Cotonou Channel, an important waterway connecting the large Nokoué Lagoon to the Atlantic Ocean in Benin. From the determination of zooplankton composition from 25-hour samples collected in July 2020, alpha diversity indices and abundance were assessed, while relationships between biotic and abiotic parameters were analyzed through Pearson correlation, analysis of variance, and principal component analysis. A total of 66 zooplankton taxa were identified, with rotifers exhibiting the highest species richness (35 taxa), while copepods dominated in abundance (71%). Zooplankton abundance varied significantly, ranging from 2 to 95 ind L−1 depending on the tidal phase. A negative correlation was found between species richness (r = −0.51, p < 0.01) and increasing salinity (3–37), indicating that higher salinity reduced diversity (r = 0.06, p > 0.05). Resilient species like Synchaeta bicornis persisted despite salinity changes. The tidal cycle structurally altered the zooplankton community, with abundance and diversity peaking at different phases, notably higher at high tide (15 ind L−1.) These initial findings underscore the complex interactions between tidal dynamics and estuarine biodiversity, suggesting the need for further research across different tidal and seasonal conditions to inform effective management and conservation efforts.
Published: 2024
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2. Characteristics of submesoscale eddy structures within mesoscale eddies in the Gulf of Mexico from 1/48° ECCO estimates

Author: Paul A. Ernst, Bulusu Subrahmanyam, Corinne B. Trott, and Alexis Chaigneau
Subjects: submesoscale, eddies, mesoscale, energy cascade, Gulf of Mexico, high resolution modelling simulations, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract: Submesoscale oceanic structures (
Published: 2023
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3. Mesoscale eddies in the southwestern tropical Atlantic

Author: Alina N. Dossa, Alex Costa da Silva, Fabrice Hernandez, Habib M. A. Aguedjou, Alexis Chaigneau, Moacyr Araujo, and Arnaud Bertrand
Subjects: mesoscale eddies, eddy characteristics, southwestern tropical Atlantic, wind stress curl, barotropic instability, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract: The southwestern tropical Atlantic is a region of complex ocean dynamic where originates the strong western boundary current system composed of North Brazil current and North Brazil undercurrent. The region includes a variety of features including the Atoll das Rocas (AR) and Fernando de Noronha (FN) ridge that may favour mesoscale eddy dynamics. However, origin, occurrence and characteristics of mesoscale eddies were still not described in the region. Using satellite altimetry data from 1993 to 2018 off Northeast Brazil (37-25°W; 13-1°S), we reconstruct eddy trajectories and analyse the main eddy surface characteristics (e.g., size, amplitude, polarity) and their spatiotemporal variations. The study reveals two distinct dynamic regions before quantifying mesoscale eddies characteristics. Approximately 2000 mesoscale eddies crossed the region during the study period, among which 76% were generated inside the region, with amplitudes and radii ranging between 1 and 2 cm and 25 and 205 km, respectively. Eddies are preferentially formed between August and September and propagate westward. In the region around the FN Archipelago (36-26°W; 6-1°S), the formation of cyclonic eddies is likely favoured by barotropic instabilities of surface currents and the wind stress curl. On the other hand, in the south of the region (36-26°W; 12-8°S), eddies formation is likely associated with the barotropic instabilities, wind stress curl and the meandering of surface currents. Based on vertical temperature and salinity profiles from Argo floats’ data, we determined that in average, the core of cyclonic eddies is centred at ~ 130 m (140 m) in the northern (southern) region while the core of anticyclonic eddies is centred at ~90 m (125 m) in the northern (southern) region. Moreover, mesoscale eddies formed in the tropical Atlantic do not connect the eastern tropical Atlantic and northeast Brazil.
Published: 2022
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4. Imprint of Mesoscale Eddies on Air-Sea Interaction in the Tropical Atlantic Ocean

Author: Habib Micaël A. Aguedjou, Alexis Chaigneau, Isabelle Dadou, Yves Morel, Ezinvi Baloïtcha, and Casimir Y. Da-Allada
Subjects: mesoscale eddies, air–sea heat exchange, precipitation, tropical Atlantic Ocean, satellite altimetry, Science
Abstract: This study investigates the effect of mesoscale eddies on air–sea heat and fresh water exchange in the tropical Atlantic Ocean (TAO) using 8 years of satellite altimetry data, combined with sea surface temperature (SST), latent and sensible heat fluxes (LHF and SHF), infrared fluxes (IRF) and precipitation (PR) data. Results indicate that approximately ∼40% of cyclonic eddies contribute to warm SST anomalies, and ∼40% of anticyclonic eddies contribute to cold SST anomalies. Eddies were found to play a role in the variability in LHF, SHF and IRF, contributing 10–35% of their total variability, with the largest contributions observed beneath the intertropical convergence zone (ITCZ) and frontal SST areas. Composite analysis of SST and heat flux anomalies over eddies suggested that the anomalies created through horizontal advection processes may not significantly impact the overall LHF, SHF and IRF over eddies, contrary to vertical processes. Despite a lack of clear correlation between heat flux and PR anomalies over eddies in the TAO, significant correlations were found beneath the ITCZ, suggesting that eddies may impact both heat fluxes and PR in the ITCZ region. This study provides an original contribution to the understanding of the impact of ocean mesoscale eddies on the atmosphere in the TAO.
Published: 2023
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5. Physicochemical Drivers of Zooplankton Seasonal Variability in a West African Lagoon (Nokoué Lagoon, Benin)

Author: Alexis Chaigneau, François Talomonwo Ouinsou, Hervé Hotèkpo Akodogbo, Gauthier Dobigny, Thalasse Tchémangnihodé Avocegan, Fridolin Ubald Dossou-Sognon, Victor Olaègbè Okpeitcha, Metogbe Belfrid Djihouessi, and Frédéric Azémar
Subjects: zooplankton, diversity and abundance, environmental parameters, seasonal variation, Nokoué Lagoon, Naval architecture. Shipbuilding. Marine engineering, VM1-989, Oceanography, GC1-1581
Abstract: This study aimed to investigate the seasonal variation of zooplankton diversity and abundance in the Nokoué Lagoon in southern Benin. Through extensive sampling, a total of 109 zooplanktonic taxa were identified and quantified. The average zooplankton abundance was found to be 60 individuals per liter, with copepods and rotifers being the most dominant groups, comprising 68.1% and 29.1% of the total abundance, respectively. The key factor identified as driving the structure of the zooplanktonic assemblages was salinity, which showed significant seasonal variation. The results revealed that during the high water period, when the lagoon was filled with fresh water, rotifers were dominant, zooplanktonic diversity was highest, and abundances were quite high. Conversely, during the low water period, when the lagoon was characterized by brackish water, diversity was minimal, and abundance decreased slightly. The study also found that some areas of the lagoon showed high abundances independent of salinity levels, suggesting that other factors such as riverine inputs or the presence of acadjas (home-made brush parks used as fish traps) may also have notable effects on the zooplankton community. Overall, the findings of this study provide valuable insights into the functioning of one of the most biologically productive lagoons in West Africa.
Published: 2023
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6. Surface Circulation and Vertical Structure of Upper Ocean Variability Around Fernando de Noronha Archipelago and Rocas Atoll During Spring 2015 and Fall 2017

Author: Alex Costa da Silva, Alexis Chaigneau, Alina N. Dossa, Gerard Eldin, Moacyr Araujo, and Arnaud Bertrand
Subjects: mesoscale activity, satellite data, western tropical Atlantic, shipboard measurements, island wake, central South Equatorial Current, Science, General. Including nature conservation, geographical distribution, QH1-199.5
Abstract: Using current, hydrographic and satellite observations collected off Northeast Brazil around the Fernando de Noronha Archipelago and Rocas Atoll during two oceanographic cruises (spring 2015 and fall 2017), we investigated the general oceanic circulation and its modifications induced by the islands. In spring 2015, the area was characterized by lower SST (26.6°C) and deep mixed-layer (∼90 m). At this depth, a strong current shear was observed between the central branch of the eastward flowing near-surface South Equatorial Current and the westward flowing South Equatorial Undercurrent. In contrast, in fall 2017, SST was higher (∼28.8°C) and the mixed-layer shallower (∼50 m). The shear between the central South Equatorial Current and the South Equatorial Undercurrent was weaker during this period. Interestingly, no oxygen-rich water from the south (retroflection of the North Brazil undercurrent) was observed in the region in fall 2017. In contrast, we revealed the presence of an oxygen-rich water entrained by the South Equatorial Undercurrent reaching Rocas Atoll in spring 2015. Beside these global patterns, island wake effects were noted. The presence of islands, in particular Fernando de Noronha, strongly perturbs central South Equatorial Current and South Equatorial Undercurrent features, with an upstream core splitting and a reorganization of single current core structures downstream of the islands. Near islands, flow disturbances impact the thermohaline structure and biogeochemistry, with a negative anomaly in temperature (−1.3°C) and salinity (−0.15) between 200 and 400 m depth in the southeast side of Fernando Noronha (station 5), where the fluorescence peak (>1.0 mg m–3) was shallower than at other stations located around Fernando de Noronha, reinforcing the influence of flow-topography. Satellite maps of sea-surface temperature and chlorophyll-a confirmed the presence of several submesoscale features in the study region. Altimetry data suggested the presence of a cyclonic mesoscale eddy around Rocas Atoll in spring 2015. A cyclonic vortex (radius of 28 km) was actually observed in subsurface (150–350 m depth) southeast of Rocas Atoll. This vortex was associated with topographically induced South Equatorial Undercurrent flow separation. These features are likely key processes providing an enrichment from the subsurface to the euphotic layer near islands, supplying local productivity.
Published: 2021
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7. From Mixing to the Large Scale Circulation: How the Inverse Cascade Is Involved in the Formation of the Subsurface Currents in the Gulf of Guinea

Author: Fernand Assene, Yves Morel, Audrey Delpech, Micael Aguedjou, Julien Jouanno, Sophie Cravatte, Frédéric Marin, Claire Ménesguen, Alexis Chaigneau, Isabelle Dadou, Gael Alory, Ryan Holmes, Bernard Bourlès, and Ariane Koch-Larrouy
Subjects: equatorial atlantic, NEUC (North Equatorial Undercurrents), SEUC (South Equatorial Undercurrents), vortices, mixing, friction, Thermodynamics, QC310.15-319, Descriptive and experimental mechanics, QC120-168.85
Abstract: In this paper, we analyse the results from a numerical model at high resolution. We focus on the formation and maintenance of subsurface equatorial currents in the Gulf of Guinea and we base our analysis on the evolution of potential vorticity (PV). We highlight the link between submesoscale processes (involving mixing, friction and filamentation), mesoscale vortices and the mean currents in the area. In the simulation, eastward currents, the South and North Equatorial Undercurrents (SEUC and NEUC respectively) and the Guinea Undercurrent (GUC), are shown to be linked to the westward currents located equatorward. We show that east of 20° W, both westward and eastward currents are associated with the spreading of PV tongues by mesoscale vortices. The Equatorial Undercurrent (EUC) brings salty waters into the Gulf of Guinea. Mixing diffuses the salty anomaly downward. Meridional advection, mixing and friction are involved in the formation of fluid parcels with PV anomalies in the lower part and below the pycnocline, north and south of the EUC, in the Gulf of Guinea. These parcels gradually merge and vertically align, forming nonlinear anticyclonic vortices that propagate westward, spreading and horizontally mixing their PV content by stirring filamentation and diffusion, up to 20° W. When averaged over time, this creates regions of nearly homogeneous PV within zonal bands between 1.5° and 5° S or N. This mean PV field is associated with westward and eastward zonal jets flanking the EUC with the homogeneous PV tongues corresponding to the westward currents, and the strong PV gradient regions at their edges corresponding to the eastward currents. Mesoscale vortices strongly modulate the mean fields explaining the high spatial and temporal variability of the jets.
Published: 2020
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8. EDDY CHARACTERISTICS AND TRACER TRANSPORTS FROM TP/ERS ALTIMETRY, IN A REGION OFFSHORE CHILE

Author: Alexis Chaigneau and Oscar Pizarro
Subjects: Oceanography, GC1-1581, Zoology, QL1-991
Abstract: Based on 9 years (1993-2001) of Sea Level Anomaly measurements from TP/ERS altimeters, we characterize the mesoscale structures of the eastern South Pacific (10-35°S, 70-100°W). Integral zonal, meridional, and temporal scales of the mesoscale activity are described geographically in the study region. The length scales increase toward the north in agreement with the increase of the Rossby radius, whereas timescales show higher values in the south of the domain. Typical values of (Lx, Ly) are around 50 km at 35°S and 80-90 km at 10°S with elongation in the zonal direction revealing the anisotropic nature of the mesoscale structures. Timescales are in the range 15-45 days. We also estimate a space-varying eddy transfer coefficient K which parameterize the effect of the eddies on the lateral tracer transports. K increases in the regions of high levels of eddy kinetic energy and is in the range of 110(7) to 410(7) cm².s-1. Considering mean climatological property gradients, we show that near the coast, the mesoscale eddies can play an important role on the long term heat and salt budgets
Published: 2004

9. Acoustics reveals the presence of a macrozooplankton biocline in the Bay of Biscay in response to hydrological conditions and predator-prey relationships.

Author: Ainhoa Lezama-Ochoa, Xabier Irigoien, Alexis Chaigneau, Zaida Quiroz, Anne Lebourges-Dhaussy, and Arnaud Bertrand
Subjects: Medicine, Science
Abstract: Bifrequency acoustic data, hydrological measurements and satellite data were used to study the vertical distribution of macrozooplankton in the Bay of Biscay in relation to the hydrological conditions and fish distribution during spring 2009. The most noticeable result was the observation of a 'biocline' during the day i.e., the interface where zooplankton biomass changes more rapidly with depth than it does in the layers above or below. The biocline separated the surface layer, almost devoid of macrozooplankton, from the macrozooplankton-rich deeper layers. It is a specific vertical feature which ties in with the classic diel vertical migration pattern. Spatiotemporal correlations between macrozooplankton and environmental variables (photic depth, thermohaline vertical structure, stratification index and chlorophyll-a) indicate that no single factor explains the macrozooplankton vertical distribution. Rather a set of factors, the respective influence of which varies from region to region depending on the habitat characteristics and the progress of the spring stratification, jointly influence the distribution. In this context, the macrozooplankton biocline is potentially a biophysical response to the search for a particular depth range where light attenuation, thermohaline vertical structure and stratification conditions together provide a suitable alternative to the need for expending energy in reaching deeper water without the risk of being eaten.
Published: 2014
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10. Correction: Oxygen: A Fundamental Property Regulating Pelagic Ecosystem Structure in the Coastal Southeastern Tropical Pacific.

Author: Arnaud Bertrand, Alexis Chaigneau, Salvador Peraltilla, Jesus Ledesma, Michelle Graco, Florian Monetti, and Francisco P. Chavez
Subjects: Medicine, Science
Published: 2012
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11. Oxygen: a fundamental property regulating pelagic ecosystem structure in the coastal southeastern tropical Pacific.

Author: Arnaud Bertrand, Alexis Chaigneau, Salvador Peraltilla, Jesus Ledesma, Michelle Graco, Florian Monetti, and Francisco P Chavez
Subjects: Medicine, Science
Abstract: BACKGROUND: In the southeastern tropical Pacific anchovy (Engraulis ringens) and sardine (Sardinops sagax) abundance have recently fluctuated on multidecadal scales and food and temperature have been proposed as the key parameters explaining these changes. However, ecological and paleoecological studies, and the fact that anchovies and sardines are favored differently in other regions, raise questions about the role of temperature. Here we investigate the role of oxygen in structuring fish populations in the Peruvian upwelling ecosystem that has evolved over anoxic conditions and is one of the world's most productive ecosystems in terms of forage fish. This study is particularly relevant given that the distribution of oxygen in the ocean is changing with uncertain consequences. METHODOLOGY/PRINCIPAL FINDINGS: A comprehensive data set is used to show how oxygen concentration and oxycline depth affect the abundance and distribution of pelagic fish. We show that the effects of oxygen on anchovy and sardine are opposite. Anchovy flourishes under relatively low oxygen conditions while sardine avoid periods/areas with low oxygen concentration and restricted habitat. Oxygen consumption, trophic structure and habitat compression play a fundamental role in fish dynamics in this important ecosystem. CONCLUSIONS/SIGNIFICANCE: For the ocean off Peru we suggest that a key process, the need to breathe, has been neglected previously. Inclusion of this missing piece allows the development of a comprehensive conceptual model of pelagic fish populations and change in an ocean ecosystem impacted by low oxygen. Should current trends in oxygen in the ocean continue similar effects may be evident in other coastal upwelling ecosystems.
Published: 2011
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12. Acoustic observation of living organisms reveals the upper limit of the oxygen minimum zone.

Author: Arnaud Bertrand, Michael Ballón, and Alexis Chaigneau
Subjects: Medicine, Science
Abstract: BACKGROUND: Oxygen minimum zones (OMZs) are expanding in the World Ocean as a result of climate change and direct anthropogenic influence. OMZ expansion greatly affects biogeochemical processes and marine life, especially by constraining the vertical habitat of most marine organisms. Currently, monitoring the variability of the upper limit of the OMZs relies on time intensive sampling protocols, causing poor spatial resolution. METHODOLOGY/PRINCIPAL FINDINGS: Using routine underwater acoustic observations of the vertical distribution of marine organisms, we propose a new method that allows determination of the upper limit of the OMZ with a high precision. Applied in the eastern South-Pacific, this original sampling technique provides high-resolution information on the depth of the upper OMZ allowing documentation of mesoscale and submesoscale features (e.g., eddies and filaments) that structure the upper ocean and the marine ecosystems. We also use this information to estimate the habitable volume for the world's most exploited fish, the Peruvian anchovy (Engraulis ringens). CONCLUSIONS/SIGNIFICANCE: This opportunistic method could be implemented on any vessel geared with multi-frequency echosounders to perform comprehensive high-resolution monitoring of the upper limit of the OMZ. Our approach is a novel way of studying the impact of physical processes on marine life and extracting valid information about the pelagic habitat and its spatial structure, a crucial aspect of Ecosystem-based Fisheries Management in the current context of climate change.
Published: 2010
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13. What are the role of mesoscale eddies in air-sea interaction and in sea surface salinity variability in the Tropical Atlantic Ocean?

Author: Habib Micaël Aguedjou, Alexis Chaigneau, Isabelle Dadou, Yves Morel, Casimir Da-Allada, and Ezinvi Baloẗcha
Abstract: The ocean kinetic energy is dominated by mesoscale eddies, which are quasi-circular structures with typical horizontal scales of 10 to 100 km and vertical extension of hundreds meters. the mesoscale eddies play significant roles in the transport and redistribution of water masses with their physical and biogeochemical properties throughout ocean. In this study, we used 8 years of satellite altimetry data, combined with sea surface temperature (SST), sea surface salinity (SSS), latent and sensible heat fluxes (LHF and SHF) and precipitation data, to investigate how mesoscale eddies impact on air-sea heat and fresh water exchange in the tropical Atlantic ocean (TAO). We show that an important fraction of eddies exhibit inverse SST anomalies, and that eddy-induced LHF and SHF anomalies are quasi-linearly proportional to SST anomalies. Moreover, eddies contribute to ~10 – 25 % of the total heat flux variability. However, no direct link has been observed between heat flux and precipitation anomalies over eddies in the TAO. Nevertheless, beneath the Intertropical Convergence Zone (ITCZ), significant correlation were found, suggesting that eddies may modulate both heat and freshwater fluxes in this region. Relative to SSS anomalies within eddies, their variability represents up to 30% of the total variability. In addition, beneath the ITCZ, freshwater fluxes would play an important role in their variability. However, oceanic processes such as horizontal and vertical advection and mixing are suspected to play a key role in the SSS variability at mesoscale beneath the ITCZ. To better understand the role of such processes, numerical modeling studies are needed for future investigations.
Published: 2023
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14. Striations and preferred eddy tracks triggered by topographic steering of the background flow in the eastern South Pacific

Author: Ali Belmadani, Emilio Concha, David Donoso, Alexis Chaigneau, François Colas, Nikolai Maximenko, and Emanuele Di Lorenzo
Published: 2017
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15. Multiscale Analysis of Geometric Planar Deformations: Application to Wild Animal Electronic Tracking and Satellite Ocean Observation Data.

Author: Ronan Fablet, Alexis Chaigneau, and Sophie Bertrand
Published: 2014
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16. From seasonal flood pulse to seiche: Multi-frequency water-level fluctuations in a large shallow tropical lagoon (Nokoué Lagoon, Benin)

Author: Alexis Chaigneau, Olaègbè Victor Okpeitcha, Yves Morel, Thomas Stieglitz, Arnaud Assogba, Morgane Benoist, Pierre Allamel, Jules Honfo, Thierry Derol Awoulmbang Sakpak, Fabien Rétif, Thomas Duhaut, Christophe Peugeot, Zacharie Sohou, 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), IRHOB, Centre de Recherches Halieutiques et Océanologiques du Bénin [Cotonou] (CRHOB), International Chair on Mathematical Physics and Applications ICMPA-Unesco Chair, UAC, Bénin (ICMPA-Unesco Chair), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), STATMarine, Laboratory of Technology and Applied Science, University Institute of Technology, University of Douala, BP 8698 Douala, Cameroon, RETIF FABIEN PHILIAN, Hydrosciences Montpellier (HSM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)
Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Aquatic Science, [SDU.STU.HY]Sciences of the Universe [physics]/Earth Sciences/Hydrology, Oceanography, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, ComputingMilieux_MISCELLANEOUS, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography
Abstract: International audience
Published: 2022
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17. Seasonal and interannual variability of salinity in a large West-African lagoon (Nokoué Lagoon, Benin)

Author: Alexis Chaigneau, Yves Morel, Zacharie Sohou, Thomas Stieglitz, Yves Pomalegni, Daouda Mama, Victor Olaègbè Okpeitcha, Université d’Abomey-Calavi (UAC), 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), International Chair on Mathematical Physics and Applications ICMPA-Unesco Chair, UAC, Bénin (ICMPA-Unesco Chair), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut de Recherches Halieutiques et Océanologiques du Bénin, Université d’Abomey-Calavi = University of Abomey Calavi (UAC), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), 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: 0106 biological sciences, Wet season, Salinity, Soil salinity, 010504 meteorology & atmospheric sciences, Stratification (water), Nokoué lagoon, Inflow, Aquatic Science, Oceanography, 01 natural sciences, stratification, Dry season, 14. Life underwater, 0105 earth and related environmental sciences, Shore, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], geography, geography.geographical_feature_category, seasonal and interannual variations, 010604 marine biology & hydrobiology, box model, tropical lagoon, 6. Clean water, 13. Climate action, Environmental science, Seawater
Abstract: International audience; Nokoué Lagoon in the South of Benin is a large intermittent coastal water body in West Africa, which supports one of the largest inland fisheries of the region. The seasonal and interannual variability of its salinity was studied, based on 3 years of monthly surveys (Dec 2017-Dec 2020). This dataset allows us to identify fine-scale salinity structures and to better understand the salinization/desalinization processes at seasonal scales. During the rainy season from May to November, under the influence of large freshwater inflows from the rivers on its northern shores, the lagoon desalinizes to a salinity of zero in October-November. During the dry season from December to April, under the effect of the ocean tide, Nokoué lagoon becomes progressively saltier, reaching typical salinities of ~25 in April. On average, the Nokoué lagoon is saltier in its southwestern part and fresher towards the river's mouths. Vertical salinity stratification is largest in December at the beginning of the main dry season. The lagoon displays a very marked interannual variation with mean surface (bottom, respectively) salinity of 25 (25) in April 2018 and 2020, respectively, against 16 (18) in April 2019. In the absence of river inflow data, a box model shows that the average salinity of the lagoon is very sensitive to small changes in river inflow (or discharge), with observed interannual differences in salinity induced by small variations of 10-15 m 3 s-1 in inflow during the dry season. During the salinization phase, the model suggests that ~30% of the seawater entering the lagoon during flood-tides remains trapped and enhances the Nokoué lagoon salinity. This model also indicates that a complete desalinization of the lagoon occurs for river inflow greater than ~50-60 m 3 s-1. The general mixing time scale of the lagoon is of 30-40 days.
Published: 2021
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18. What can we learn from observed temperature and salinity isopycnal anomalies at eddy generation sites? Application in the Tropical Atlantic Ocean

Author: Alexis Chaigneau, I. Dadou, C. Y. Da-Allada, C. Pegliasco, E. Baloïtcha, H. M. A. Aguedjou, Yves Morel, 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), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), 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: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Isopycnal, 010504 meteorology & atmospheric sciences, isopycnal temperature/salinity anomalies, eddy generation mechanisms, 010505 oceanography, potential vorticity, Temperature salinity diagrams, mesoscale eddies, Tropical Atlantic, Oceanography, 01 natural sciences, Mesoscale eddies, Geophysics, 13. Climate action, Space and Planetary Science, Geochemistry and Petrology, Potential vorticity, tropical Atlantic Ocean, Earth and Planetary Sciences (miscellaneous), 14. Life underwater, Geology, 0105 earth and related environmental sciences
Abstract: International audience;  At their generation site, 50% of observed eddies have non-significant isopycnal temperature/salinity (θ/S) anomalies in the TAO.  On density-coordinates, both CEs and AEs can exhibit significant positive, negative or non-significant isopycnal θ/S anomalies.  We discuss the relationship between isopycnal θ/S and PV anomalies and how they can inform us on their generation mechanisms.
Published: 2021
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19. Terrestrial or oceanic forcing? Water level variations in coastal lagoons constrained by river inflow and ocean tides

Author: Yves Morel, Alexis Chaigneau, Victor Olaègbè Okpeitcha, Thomas Stieglitz, Arnaud Assogba, Thomas Duhaut, Fabien Rétif, Christophe Peugeot, Zacharie Sohou, 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), Université d’Abomey-Calavi = University of Abomey Calavi (UAC), Centre européen de recherche et d'enseignement des géosciences de l'environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut de Recherches Halieutiques et Océanologiques du Bénin, RETIF FABIEN PHILIAN, Hydrosciences Montpellier (HSM), and Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)
Subjects: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Tide, River flux, Lagoon, Water level, Water Science and Technology
Abstract: The study concerns the water level (WL) evolution in lagoons under the influence of tides and river fluxes. We derive new approximate analytical solutions of the Stigebrandt (1980) equations and apply them to the Nokoué Lagoon (Benin), a large tropical coastal lagoon fed by substantial river input.
Published: 2022
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20. Eddy‐Induced Temperature and Salinity Variability in the Arabian Sea

Author: Corinne B. Trott, Bulusu Subrahmanyam, Alexis Chaigneau, and Heather L. Roman‐Stork
Subjects: Geophysics, Oceanography, Eddy, Temperature salinity diagrams, General Earth and Planetary Sciences, Monsoon, Geology
Published: 2019
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21. What can we learn from observed temperature and salinity isopycnal anomalies at eddy generation sites? Application in the Tropical Atlantic Ocean

Author: E. Baloïtcha, C. Pegliasco, C. Y. Da-Allada, Yves Morel, H. M. A. Aguedjou, Alexis Chaigneau, and I. Dadou
Subjects: Isopycnal, Oceanography, Temperature salinity diagrams, Tropical Atlantic, Geology
Abstract: Potential vorticity (PV) is a key parameter to analyze the generation and dynamics of mesoscale eddies. Numerical studies have shown how adiabatic (displacement of particles within a background gradient of PV) and diabatic (diapycnal mixing and friction) processes can be involved in the generation of localized PV anomalies and vortices. Such processes are however difficult to evaluate in the ocean because PV is difficult to evaluate at mesoscale. In this study, we argue that qualitative analysis can be done, based on the link between PV anomalies and isopycnal temperature/salinity anomalies (Ɵ’/S’). Indeed, in the ocean, eddies created by diapycnal mixing or isopycnal advection of water-masses, are associated with PV anomalies and significant isopycnal Ɵ’/S’. In contrast, eddies created by friction are associated with PV anomalies but without isopycnal Ɵ’/S’. In this study, based on 18 years of satellite altimetry data and vertical Ɵ/S profiles acquired by Argo floats, we analyze the isopycnal Ɵ’/S’ within new-born eddies in the tropical Atlantic Ocean (TAO) and discuss the possible mechanisms involved in their generation. Our results show that on density-coordinates system, both anticyclonic (AEs) and cyclonic (CEs) eddies can exhibit positive, negative, or non-significant Ɵ’/S’. Almost half of the sampled eddies do not have significant Ɵ’/S’ at their generation site, indicating that frictional effects probably play a significant role in the generation of their PV anomalies. The other half of eddies, likely generated by diapycnal mixing or isopycnal advection, exhibits significant positive or negative anomalies with typical Ɵ’ of ±0.5°C. More than 70% of these significant eddies are subsurface-intensified, having their cores below the seasonal pycnocline. Refined analyses of the vertical structure of new-born eddies in three selected subregions of the TAO where the strongest anomalies were observed, show the dominance of cold (warm, respectively) subsurface AEs (CEs) likely due to isopycnal advection of large scale PV and temperature.
Published: 2021
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22. Detection and tracking of mesoscale eddies in the Mediterranean Sea: A comparison between the Sea Level Anomaly and the Absolute Dynamic Topography fields

Author: Cori Pegliasco, Rosemary Morrow, Franck Dumas, Alexis Chaigneau, 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), Service Hydrographique et Océanographique de la Marine (SHOM), and Ministère de la Défense
Subjects: Atmospheric Science, 010504 meteorology & atmospheric sciences, Mesoscale meteorology, Aerospace Engineering, 01 natural sciences, Mediterranean sea, Mesoscale eddies, 0103 physical sciences, Mediterranean Sea, Bathymetry, Sea level, Altimeter, 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, Orographic lift, Astronomy and Astrophysics, Ocean surface topography, Geophysics, Eddy, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Climatology, Spatial ecology, General Earth and Planetary Sciences, Altimetry, Geology
Abstract: International audience; Mediterranean Sea eddies are often generated in fixed geographical locations linked to either bathymetric fluctuations, coastline changes, instabilities around islands, or orographic wind forcing. Because of that, the mean circulation exhibits features with the same special scales as the mesoscale field. We provide here a first comparison of eddies detected and tracked using two altimetry products, the Sea Level Anomaly (SLA) and the Absolute Dynamic Topography (ADT), from 2000 to 2015. We showed that more individual eddies and trajectories are detected in the SLA data than in the ADT, having larger radius but lower Eddy Kinetic Energy. The spatial distribution of the mesoscale activity is different between the two data sets: the ADT-detected eddies closely follow the Mean Dynamic Topography (MDT) patterns which include the mean eddy generation sites whereas the SLA-detected eddies show more spatial homogeneity. The larger eddies are generally well detected in both the ADT or the SLA fields, but the numerous smaller and coastal eddies detected in the SLA fields have a tendency to mismatch the ADT detected eddies. Only 20-30% of eddies are detected exclusively in the SLA or the ADT product (i.e. have no collocation in the other field), whereas to 65-80% of the eddies are detected both in the SLA and the ADT fields. The Ierapetra Eddy is a typical example of the limitation of the SLA-detected eddies, as this orographically controlled feature is present in the MDT and thus leads to an artificial cyclonic eddy in the SLA field that shifts around its most frequent position. This study recommends the use of ADT fields for the detection of mesoscale structures in the Mediterranean Sea where the mean circulation and these mesoscale features have the same spatial scale and intensity, and similarly for any other ocean regions where the MDT contains mesoscale patterns. Yet the ADT fields depend on the accuracy of the MDT, and the altimeter-based SLA fields may be preferable in specific locations where the MDT is not reliable.
Published: 2021
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23. Near-surface western boundary circulation off Northeast Brazil

Author: Alina N. Dossa, Arnaud Bertrand, Moacyr Araujo, Gérard Eldin, Alex Costa da Silva, Alexis Chaigneau, Universidade Federal de Pernambuco [Recife] (UFPE), 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), Université d’Abomey-Calavi (UAC), Institut national des sciences de l'Univers (INSU - CNRS), MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), 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 d’Abomey-Calavi = University of Abomey Calavi (UAC), and Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)
Subjects: 0106 biological sciences, thermocline, 010504 meteorology & atmospheric sciences, [SDE.MCG]Environmental Sciences/Global Changes, Mesoscale meteorology, Aquatic Science, Tropical Atlantic, 01 natural sciences, Acoustic Doppler current profiler, 14. Life underwater, Altimeter, currents, 0105 earth and related environmental sciences, Orographic lift, Shore, geography, geography.geographical_feature_category, Continental shelf, 010604 marine biology & hydrobiology, adcp, upper-layer, Geology, ADCP, ocean, North Brazil Current, Oceanography, 13. Climate action, flow, Mesoscale activity, Western Tropical Atlantic, Flow-topography interaction, North Brazil Undercurrent, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, south-atlantic, Thermocline, tropical atlantic
Abstract: WOS:000604185400001; International audience; In the tropical Atlantic Ocean, the North Brazil Undercurrent (NBUC) and the North Brazil Current (NBC) play important roles as near-surface northward paths for the Atlantic meridional overturning circulation. To investigate the meridional evolution of the near-surface western boundary circulation in that region, two surveys were carried out off Northeast Brazil during austral spring 2015 and fall 2017, periods that we show to be representative of typical conditions for the spring and fall seasons. Using conductivity temperature depth oxygen probe and ship-mounted acoustic Doppler current profiler measurements, altimetry data, and numerical reanalysis products, we examine the spatiotemporal variability of the NBUC, providing a comprehensive view of the circulation, including NBUC-NBC transition and the potential impact of mesoscale eddies. The NBUC originating south of 10 degrees S flows equatorward over the continental slope. NBUC mean velocity, transport and vertical extent of the velocity core were higher in spring 2015 (0.81 m s(-1), 15.6 Sv, and \textgreater400 m) than in fall 2017 (0.65 m s(-1), 11.0 Sv, and similar to 300 m). The upper limit of the NBUC velocity core rose slightly from 160 m at 9 degrees S to 105 m depth at 6 degrees S. This pattern is associated with a northward increase in current velocity from 0.7 m s(-1) at 9 degrees S to 1 m s(-1) at 5 degrees S. The orographic effect shifts the flow from northeastward south of 7.5 degrees S to northwestward north of 7.5 degrees S, following the shoreline. Besides, altimetry data show that this flow can be locally influenced by mesoscale activity. Farther north, at similar to 4.8 degrees S, data obtained in fall 2017 show that the central branch of the South Equatorial Current (cSEC) enters into the western boundary system where it coalesces with the NBUC to form the NBC, flowing toward the Caribbean Sea. Finally, in fall, the NBUC retroflection does not feed the South Equatorial Undercurrent (SEUC), which, instead originates from retroflections of the cSEC and the equatorial branch of the South Equatorial Current (eSEC).
Published: 2021
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24. From Mixing to the Large Scale Circulation: How the Inverse Cascade Is Involved in the Formation of the Subsurface Currents in the Gulf of Guinea

Author: Isabelle Dadou, Bernard Bourlès, Claire Ménesguen, Julien Jouanno, Yves Morel, Sophie Cravatte, Ryan M. Holmes, Fernand Assene, Micael Aguedjou, Audrey Delpech, Frédéric Marin, Ariane Koch-Larrouy, Gaël Alory, Alexis Chaigneau, 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), Université de Douala, Université d’Abomey-Calavi (UAC), Laboratoire d'Océanographie Physique et Spatiale (LOPS), 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), University of New South Wales [Sydney] (UNSW), Instrumentation, Moyens Analytiques, Observatoires en Géophysique et Océanographie (IMAGO) (IMAGO), Institut de Recherche pour le Développement (IRD [France-Ouest]), 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 d’Abomey-Calavi = University of Abomey Calavi (UAC), and Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Pycnocline, 010504 meteorology & atmospheric sciences, friction, Subsurface currents, Mesoscale meteorology, Zonal and meridional, lcsh:Thermodynamics, 01 natural sciences, SEUC, Potential vorticity, lcsh:QC310.15-319, equatorial atlantic, mixing, 14. Life underwater, friction 19, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, lcsh:QC120-168.85, 0105 earth and related environmental sciences, Fluid Flow and Transfer Processes, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Equatorial Atlantic, 010505 oceanography, Advection, Mechanical Engineering, vortices, Geophysics, Condensed Matter Physics, Vortex, 13. Climate action, Anticyclone, NEUC (North Equatorial Undercurrents), SEUC (South Equatorial Undercurrents), NEUC, lcsh:Descriptive and experimental mechanics, Geology
Abstract: In this paper, we analyse the results from a numerical model at high resolution. We focus on the formation and maintenance of subsurface equatorial currents in the Gulf of Guinea and we base our analysis on the evolution of potential vorticity (PV). We highlight the link between submesoscale processes (involving mixing, friction and filamentation), mesoscale vortices and the mean currents in the area. In the simulation, eastward currents, the South and North Equatorial Undercurrents (SEUC and NEUC respectively) and the Guinea Undercurrent (GUC), are shown to be linked to the westward currents located equatorward. We show that east of 20&deg, W, both westward and eastward currents are associated with the spreading of PV tongues by mesoscale vortices. The Equatorial Undercurrent (EUC) brings salty waters into the Gulf of Guinea. Mixing diffuses the salty anomaly downward. Meridional advection, mixing and friction are involved in the formation of fluid parcels with PV anomalies in the lower part and below the pycnocline, north and south of the EUC, in the Gulf of Guinea. These parcels gradually merge and vertically align, forming nonlinear anticyclonic vortices that propagate westward, spreading and horizontally mixing their PV content by stirring filamentation and diffusion, up to 20&deg, W. When averaged over time, this creates regions of nearly homogeneous PV within zonal bands between 1.5&deg, and 5&deg, S or N. This mean PV field is associated with westward and eastward zonal jets flanking the EUC with the homogeneous PV tongues corresponding to the westward currents, and the strong PV gradient regions at their edges corresponding to the eastward currents. Mesoscale vortices strongly modulate the mean fields explaining the high spatial and temporal variability of the jets.
Published: 2020
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25. Erosion of the Subsurface Salinity Maximum of the Loop Current Eddies From Glider Observations and a Numerical Model

Author: M. Tenreiro, E. Pallàs‐Sanz, Alexis Chaigneau, Julio Candela, Julien Jouanno, and R. Sosa-Gutierrez
Subjects: Salinity, Loop (topology), Geophysics, Eddy, Space and Planetary Science, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), Erosion, Glider, Current (fluid), Oceanography, Atmospheric sciences, Geology
Published: 2020
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26. Eddy Surface Characteristics and Vertical Structure in the Gulf of Mexico from Satellite Observations and Model Simulations

Author: Bulusu Subrahmanyam, Corinne B. Trott, Alexis Chaigneau, Richard J. Brokaw, 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), 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: Surface (mathematics), Gulf of Mexico, HYCOM, Oceanography, Atmospheric sciences, Physics::Geophysics, SST, salinity, Physics::Fluid Dynamics, Geophysics, Eddy, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), chlorophyll, Satellite, eddies, Physics::Atmospheric and Oceanic Physics, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Geology
Abstract: International audience; The Gulf of Mexico exhibits strong circulation due to the Loop Current System, along with high mesoscale eddy activity. In order to investigate eddy characteristics, we apply an automatic eddy-tracking algorithm to absolute dynamic topography maps and analyze the spatial distribution and evolution of eddy attributes including amplitude, radius, and eddy kinetic energy. The Loop Current region in the eastern Gulf of Mexico is an area of robust eddy generation for both cyclonic and anticyclonic eddies. Anticyclonic eddies were generally characterized by smaller amplitudes and larger radii when compared to their cyclonic counterparts. We also examine eddy surface properties including temperature and salinity anomalies as well as chlorophyll-a concentration and observe how these properties vary between the eastern and western Gulf of Mexico. Persistent features such as the Loop Current System and coastal low-salinity, highly biologically productive waters dominate eddy properties in the eastern side of the basin. We also apply the eddy-tracking algorithm to a regional Hybrid Coordinate Ocean Model validated using Argo floats. We find that this model accurately reflects surface characteristics in the mesoscale eddy field as well as the mean vertical eddy structure and use it to extend our analysis of eddy properties with depth. We find that subsurface characteristics of density, salinity, temperature, and velocities vary greatly between eddies in the eastern and western Gulf of Mexico. Through composite analysis of both surface and subsurface eddy properties, we gain a more complete picture of the mechanisms behind the observable characteristics of these eddies.
Published: 2020
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27. Degradation of groundwater quality in expanding cities in West Africa. A case study of the unregulated shallow aquifer in Cotonou

Author: Roland Silmer, Abdoukarim Alassane, Stéphane Ruy, Daouda Mama, Akilou Socohou, Honoré Houéménou, Alexis Chaigneau, Milanka Babic, Marc Leblanc, Gauthier Dobigny, Philippe Gauthier, Sarah Tweed, Henri-Joël Dossou, Sylvestre Badou, Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes (EMMAH), Avignon Université (AU)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), University of Abomey Calavi (UAC), Gestion de l'Eau, Acteurs, Usages (UMR G-EAU), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Centre de Biologie pour la Gestion des Populations (UMR CBGP), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université de Montpellier (UM)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Ecole Polytechnique d'Abomey Calavi (EPAC), 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 Recherches Halieutiques et Océanologiques du Bénin, International Chair in Mathematical Physics and Applications (ICMPA-UNESCO Chair), The authors owe much gratitude to hydrogeology laboratory of Avignon University, EPAC/LARBA and IRD/CBGP for the full financial and logistical support of this work., Université d’Abomey-Calavi = University of Abomey Calavi (UAC), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Université de Montpellier (UM)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro - Montpellier SupAgro, Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), 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: Pollution, 010504 meteorology & atmospheric sciences, Sanitation, media_common.quotation_subject, [SDV]Life Sciences [q-bio], Population, 0207 environmental engineering, Septic tank, Aquifer, 02 engineering and technology, 01 natural sciences, Urbanization, 11. Sustainability, Sewerage, 020701 environmental engineering, education, Groundwater, 0105 earth and related environmental sciences, Water Science and Technology, media_common, 2. Zero hunger, geography, education.field_of_study, geography.geographical_feature_category, Salinization, 6. Clean water, 13. Climate action, Sewerage and septic tank contamination, Environmental science, Recharge and discharge, Water resource management
Abstract: International audience; Highlights• Predominant drivers of the unregulated shallow aquifer degradation in Cotonou were analysed using major ions, Cl/Br molar ratios and stables isotopes as environmental tracers. Vulnerability of this unofficial groundwater resource is due to either salinization or sewage leakage, which is temporally and spatially variable.• Increasing risks from sewage and septic tank leakage during the wet season in neighbourhoods located in discharge areas compared with increasing risk during the dry season in the recharge area.• Mixing with pond water and saline Lake Nokoué water highlight increased risks of shallow groundwater salinization during the dry and small wet seasons in discharge areas.AbstractIn Cotonou, as in many expanding West African cities, major population growth and infrastructural development has not kept up with informal settlement development onto floodable plains and marshes. The population of the slum, which makes up about 60% of the city's inhabitants, is highly disadvantaged and vulnerable to rising sea levels, flooding, sanitation and waste management issues. However, the risks associated with the use of contaminated shallow groundwater for domestic purposes are less recognised. Our study demonstrates that, in many instances, the cheaper option of the use of shallow groundwater from the coastal Quaternary aquifer for domestic purposes represents a significant risk for the poorer residents of Cotonou through the voluntary (drinking) or non-volontary (dish washing, cooking) consumption of this unmonitored and untreated water resource. In the 3 neighbourhoods surveyed, environmental tracers (major ions, Cl/Br molar ratios and stables isotopes) showed that this shallow aquifer is degraded by seawater intrusion as well as septic and sewerage contamination. In particular, the higher NOx concentrations correspond to ranges associated with sewerage and septic tank effluent pollution and the major ion concentrations and delta H-2-delta O-18 signatures showed that high salinity values are where groundwater mixes with saline Lake Nokoue water. The population using this resource from local wells should be made aware of seasonal changes in groundwater contamination and potential health risks associated with sewerage and septic tank contamination.
Published: 2020
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28. Eddy Tracking in the Northwestern Indian Ocean During Southwest Monsoon Regimes

Author: Alexis Chaigneau, Thierry Delcroix, Corinne B. Trott, and Bulusu Subrahmanyam
Subjects: Indian ocean, Geophysics, Oceanography, 010504 meteorology & atmospheric sciences, 010505 oceanography, General Earth and Planetary Sciences, Sea-surface height, Monsoon, Tracking (particle physics), 01 natural sciences, Geology, 0105 earth and related environmental sciences
Published: 2018
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29. Complementary Use of Glider Data, Altimetry, and Model for Exploring Mesoscale Eddies in the Tropical Pacific Solomon Sea

Author: L. Gourdeau, Alexis Chaigneau, William S. Kessler, Jacques Verron, and Sophie Cravatte
Subjects: Water mass, 010504 meteorology & atmospheric sciences, 010505 oceanography, Glider, Mesoscale meteorology, Oceanography, 01 natural sciences, Boundary current, Current (stream), Geophysics, Eddy, Space and Planetary Science, Geochemistry and Petrology, Climatology, Earth and Planetary Sciences (miscellaneous), Altimeter, Thermocline, Geology, 0105 earth and related environmental sciences
Abstract: Mesoscale activity is an important component of the Solomon Sea circulation that interacts with the energetic low latitude western boundary currents of the South tropical Pacific Ocean carrying waters of subtropical origin before joining the equatorial Pacific. Mixing associated with mesoscale activity could explain water mass transformation observed in the Solomon Sea that likely impacts El Nino Southern Oscillation dynamics. This study makes synergetic use of glider data, altimetry, and high-resolution model for exploring mesoscale eddies, especially their vertical structures, and their role on the Solomon Sea circulation. The description of individual eddies observed by altimetry and gliders provides the first elements to characterize the 3D structure of these tropical eddies, and confirms the usefulness of the model to access a more universal view of such eddies. Mesoscale eddies appear to have a vertical extension limited to the Surface Waters (SW) and the Upper Thermocline Water (UTW), i.e. the first 140-150 m depth. Most of the eddies are nonlinear, meaning that eddies can trap and transport water properties. But they weakly interact with the deep New Guinea Coastal Undercurrent that is a key piece of the equatorial circulation. Anticylonic eddies are particularly efficient to advect salty and warm SW coming from the intrusion of equatorial Pacific waters at Solomon Strait, and to impact the characteristics of the New Guinea Coastal Current. Cyclonic eddies are particularly efficient to transport South Pacific Tropical Water (SPTW) anomalies from the North Vanuatu Jet and to erode by diapycnal mixing the high SPTW salinity.
Published: 2017
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30. Eddies in the Tropical Atlantic Ocean and their seasonal variability

Author: I. Dadou, H. M. A. Aguedjou, Gaël Alory, Alexis Chaigneau, Yves Morel, 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), 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: [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], 010504 meteorology & atmospheric sciences, Ocean current, Mesoscale meteorology, mesoscale eddies, Tropical Atlantic, 010502 geochemistry & geophysics, 01 natural sciences, Latitude, Current (stream), Geophysics, Oceanography, seasonal variability, Eddy, 13. Climate action, tropical Atlantic Ocean, barotropic instability, altimetry, General Earth and Planetary Sciences, Altimeter, Geology, Sea level, 0105 earth and related environmental sciences
Abstract: We study mesoscale eddy characteristics in the tropical Atlantic Ocean, using 23 years of daily altimetry sea level anomalies. Eddies are mainly generated in the eastern boundary upwelling systems and in the Brazil Current region. Their westward propagation speed reaches 20 cm/s in equatorial areas, decreasing with latitudes. They present typical amplitudes of 1-5 cm. The largest and most energetic eddies are observed in the equatorial region, especially in the North Brazil Current (NBC) retroflection. The seasonal cycle of the eddy characteristics shows higher amplitudes along the NBC retroflection and the western part of the North Equatorial Countercurrent. A new criterion, based on altimetry data, determines the probability that barotropic instability of mean surface currents is responsible for eddy generation. We find a strong likelihood that the latter plays a key role along the North Equatorial Countercurrent, whereas other mechanisms must be invoked for the NBC region.
Published: 2019
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31. Subsurface Fine-Scale Patterns in an Anticyclonic Eddy Off Cap-Vert Peninsula Observed From Glider Measurements

Author: Nicolas Kolodziejczyk, Claire Gourcuff, Gerd Krahmann, Patrice Brehmer, Philippe Estrade, Xavier Capet, Pierre Testor, Saliou Faye, Malick Wade, Florian Schütte, Vincent Echevin, Laurent Mortier, Johannes Karstensen, Alexis Chaigneau, Alban Lazar, Laboratoire d'Océanographie Physique et Spatiale (LOPS), 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), Variabilité de l'Océan et de la Glace de mer (VOG), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), Océan et variabilité du climat (VARCLIM), Processus et interactions de fine échelle océanique (PROTEO), Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), 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), Université Gaston Berger de Saint-Louis Sénégal (UGB), Institut Sénégalais de Recherches Agricoles [Dakar] (ISRA), Laboratoire de Physique de l'Atmosphère et de l'Océan Siméon Fongang (LPAO-SF), École Supérieure Polytechnique de Dakar (ESP), Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD)-Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD), Institut de Recherche pour le Développement (IRD), Leibniz-Institut für Meereswissenschaften (IFM-GEOMAR), EGU, 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), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), GEOMAR - Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Laboratoire des sciences de l’Atmosphère et de l’Océan, Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD), 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 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), Campus International UCAD-IRD [Dakar, Senegal], European Project: 603521,EC:FP7:ENV,FP7-ENV-2013-two-stage,PREFACE(2013), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), 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 [Sénégal]), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), European Project: 635359,H2020,H2020-BG-2014-2,BRIDGES(2015), European Project: 633211,H2020,H2020-BG-2014-2,AtlantOS(2015), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), and Pinsard, Françoise
Subjects: Water mass, 010504 meteorology & atmospheric sciences, meoscale eddy, [PHYS.PHYS.PHYS-GEO-PH] Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], tropical Atlantic, Temperature salinity diagrams, submesoscale, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], glider, Tropical Atlantic, Oceanography, 01 natural sciences, Cape verde, stirring, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), 14. Life underwater, glider measurements, 0105 earth and related environmental sciences, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, geography, geography.geographical_feature_category, 010505 oceanography, Continental shelf, ACL, Geophysics, Eddy, Space and Planetary Science, Anticyclone, OMZ, Thermohaline circulation, measurements, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Geology
Abstract: International audience; Glider measurements acquired along four transects between Cap-Vert Peninsula and theCape Verde archipelago in the eastern tropical North Atlantic during March–April 2014 were used to investigate fine-scale stirring in an anticyclonic eddy. The anticyclone was formed near 12°N off the continental shelf and propagated northwest toward the Cape Verde islands. At depth, between 100 and–400 m, the isolated anticyclone core contained relatively oxygenated, low-salinity South Atlantic CentralWater, while the surrounding water masses were saltier and poorly oxygenated. The dynamical and thermohaline subsurface environment favored the generation offine-scale horizontal and vertical temperature and salinity structures in and around the core of the anticyclone. These features exhibited horizontal scales of O(10–30 km) relatively small with respect to the eddy radius of O(150 km). The vertical scales of O(5–100 m) were associated to density-compensated gradient. Spectra of salinity and oxygen along isopycnals revealed a slope of around k-2in the 10- to 100-km horizontal scale range.Further analyses suggest that the fine-scale structures are likely related to tracer stirring processes. Such mesoscale anticyclonic eddies and the embedded fine-scale tracers in and around them could play a major role in the transport of South Atlantic Central Water masses and ventilation of the North Atlantic Oxygen Minimum Zone.
Published: 2019
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32. Eddy‐Induced Salinity Changes in the Tropical Pacific

Author: D. Soviadan, Cori Pegliasco, Jacqueline Boutin, Alexis Chaigneau, Thierry Delcroix, 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 Recherches Halieutiques et Océanologiques du Bénin, International Chair of Mathematical Physics and Applications (ICMPA-UNESCO), University of Abomey Calavi (UAC), Processus et interactions de fine échelle océanique (PROTEO), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU), CNES ID 4626, 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 d’Abomey-Calavi = University of Abomey Calavi (UAC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)
Subjects: 010504 meteorology & atmospheric sciences, Mesoscale meteorology, Zonal and meridional, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Oceanography, 01 natural sciences, Physics::Geophysics, Physics::Fluid Dynamics, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), 14. Life underwater, Sea level, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, 010505 oceanography, Advection, SSS, Salinity, Geophysics, Eddy, 13. Climate action, Space and Planetary Science, Anticyclone, [SDU]Sciences of the Universe [physics], Climatology, Geology
Abstract: International audience; The signature of westward propagating mesoscale eddies in sea surface salinity (SSS) is analyzed for the tropical Pacific by collocating 7 years (2010–2016) of Soil Moisture and Ocean Salinity SSS satellite data with coherent mesoscale eddies automatically identified and tracked from altimetry‐derived sea level anomalies. First, the main characteristics of the long‐lived coherent eddies are inferred from sea level anomalies maps. Then, the mean signature of the mesoscale eddies on SSS is depicted for the whole tropical Pacific before focusing in regions centered around the central and eastern parts of the tropical North Pacific. In these areas, composite analyses based on thousands of eddies reveal regionally dependent eddy impacts with opposite SSS anomalies for cyclonic and anticyclonic eddies. In the central region, where the largest meridional SSS large‐scale gradients and smallest eddy amplitudes are observed, results show dipole‐like SSS changes with maximum anomalies on the leading edge of the composite eddy. In contrast, in the eastern region, where the largest near‐surface vertical salinity gradients and largest eddy amplitudes are observed, the composite eddy shows monopole‐like SSS changes with maximum anomalies near the composite eddy center. These distinct dipole/monopole SSS patterns suggest the dominant role of horizontal advection and vertical processes in the central and eastern regions, respectively. Other possible explanations, notably one involving the contrasted eddy amplitudes of the two regions, are discussed.
Published: 2019
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33. Upper ocean hydrology of the Northern Humboldt Current System at seasonal, interannual and interdecadal scales

Author: Carmen Grados, Alexis Chaigneau, Noel Dominguez, Vincent Echevin, Instituto del Mar del Peru (IMARPE), 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), Processus et interactions de fine échelle océanique (PROTEO), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), International Joint Laboratory-Dynamics of the Humboldt Current system (LMI-DISCOH), 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 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), 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)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)
Subjects: 0106 biological sciences, Water mass, 010504 meteorology & atmospheric sciences, Temperature salinity diagrams, Geostrophic currents, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Seasonal variations, Aquatic Science, 01 natural sciences, Latitude, Water masses, Geostrophic current, 14. Life underwater, 0105 earth and related environmental sciences, Interdecadal variability, Hydrology, 010604 marine biology & hydrobiology, Geology, North Humboldt Current System, La Niña, Oceanography, 13. Climate action, Upwelling, Longitude, ENSO, Thermocline
Abstract: Since the 1960s, the Instituto del Mar del Peril (IMARPE) collected tens of thousands of in-situ temperature and salinity profiles in the Northern Humboldt Current System (NHCS). In this study, we blend this unique database with the historical in-situ profiles available from the World Ocean Database for the period 1960-2014 and apply a four-dimensional interpolation scheme to construct a seasonal climatology of temperature and salinity of the NHCS. The resulting interpolated temperature and salinity fields are gridded at a high spatial resolution (0.1 degrees x 0.1 degrees in latitude/longitude) between the surface and 1000 m depth, providing a detailed view of the hydrology and geostrophic circulation of this region. In particular, the mean distribution and characteristics of the main water-masses in the upper ocean of the NHCS are described, as well as their seasonal variations between austral summer and winter. The coastal upwelling region is well documented due to the increased data density along 3 highlighted cross-shore vertical sections off Paita (similar to 5 degrees S), Chimbote (similar to 9 degrees S) and San Juan (similar to 16.5 degrees S). The large and long-term database also allowed us, through a composite analysis, to investigate the impact of the eastern Pacific El Nino and La Nina events on the NHCS hydrology. On average, during these periods, large temperature (+/- 3-4 degrees C) and salinity (+/- 0.1-0.2) anomalies are observed, impacting the water column of the coastal ocean off Peru down to 100-200 m depth. At 100 km from the coast, these anomalies are associated with a maximum deepening (shoaling, respectively) of the thermocline of 60 m (25 m) during composite El Nino (La Nina) events. At interdecadal scale, a similar approach reveals sea-surface temperature variations of +/- 0.5 degrees C, associated with a deepening (shoaling) of the thermocline of 5-10 m during warm (cold) periods.
Published: 2018
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34. Long-term changes in the breeding seasonality of Peruvian seabirds and regime shifts in the Northern Humboldt Current System

Author: Arnaud Bertrand, Christophe Barbraud, Giannina Passuni, Ramiro Castillo, Sophie Bertrand, Alexis Chaigneau, Jesus Ledesma, Ricardo Oliveros-Ramos, Marilú Bouchon, Nelson Mandela University, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), 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), MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Instituto del Mar del Peru (IMARPE), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Institute of Research for Development Department - Laboratory for Studies in Geophysics and Spatial Oceanography (LEGOS), Institut National de la Recherche Agronomique (INRA)-Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-Université de La Rochelle (ULR)
Subjects: 0106 biological sciences, NHCS, [SDE.MCG]Environmental Sciences/Global Changes, Aquatic Science, 010603 evolutionary biology, 01 natural sciences, Predation, Engraulis, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Anchovy, biology.animal, medicine, Northern Humboldt Current System, Peruvian booby, 14. Life underwater, Environmental cues, Phalacrocorax bougainvillii, Ecology, Evolution, Behavior and Systematics, Sula variegata, Ecology, biology, 010604 marine biology & hydrobiology, Cormorant, Onset of breeding, Seasonality, biology.organism_classification, medicine.disease, Fishery, Pelican, 13. Climate action, Oxycline depth, Pelecanus thagus, Seabird, [SDE.BE]Environmental Sciences/Biodiversity and Ecology
Abstract: International audience; In the highly productive Northern Humboldt Current System, 3 seabird species, the Guanay cormorant Phalacrocorax bougainvillii, the Peruvian booby Sula variegata and the Peruvian pelican Pelecanus thagus, commence breeding in austral spring, coinciding with the lowest availability of their prey, the Peruvian anchovy Engraulis ringens. This strategy ensures the matching of increased prey availability when young achieve independence in summer. This pattern was observed during the last decade when anchovy was abundant. However, over the last century, the abundance of anchovy has varied widely due to contrasting interdecadal regimes in oceanographic conditions and fishing activity. We hypothesized that these regime shifts affected the abundance and availability of prey and may have conditioned the breeding seasonality of seabirds. We examined the timing and magnitude of the onset of breeding using dynamic occupancy models and related these parameters to the seasonality of oceanographic conditions, abundance of anchovy and fishing pressure. During a regime of lower anchovy abundance (1977-1990), cormorants showed the highest flexibility, adjusting the timing of breeding from spring to winter and skipping reproduction in the worst conditions. Boobies showed the lowest flexibility, maintaining the same magnitude and timing of onset of breeding in spring. Pelicans showed intermediate flexibility, foregoing breeding during the worst conditions, but maintaining the onset of breeding in spring. The 3 species used sea surface temperature as a cue for the initiation of breeding. Furthermore, given their better diving abilities, cormorants could monitor prey availability changes associated with the reversion in the seasonality of the oxycline depth.
Published: 2018
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35. Observed Characteristics and Vertical Structure of Mesoscale Eddies in the Southwest Tropical Pacific

Author: Lydia Keppler, L. Gourdeau, Alexis Chaigneau, Awnesh M. Singh, Cori Pegliasco, and Sophie Cravatte
Subjects: Water mass, 010504 meteorology & atmospheric sciences, Oceanography, 01 natural sciences, southwest Pacific, Geochemistry and Petrology, Ocean gyre, Earth and Planetary Sciences (miscellaneous), Bathymetry, 14. Life underwater, Argo, 0105 earth and related environmental sciences, geography, geography.geographical_feature_category, 010505 oceanography, mesoscale eddies, argo floats, satellite altimetry, Salinity, Geophysics, Eddy, 13. Climate action, Space and Planetary Science, Anticyclone, Thermocline, Geology
Abstract: In the Southwest Pacific Ocean, waters transit from the subtropical gyre before being redistributed equatorward and poleward. While the mean pathways are known, the contribution to the mixing and transport of the water from mesoscale eddies has not been comprehensively investigated. In this research, satellite altimetry data, combined with an eddy detection and tracking algorithm is used to investigate the distribution and surface characteristics of mesoscale eddies in this region of complex bathymetry (10 degrees S-30 degrees S, 140 degrees E-190 degrees E). Detected eddies are then colocalized with in situ data from Argo floats to determine their vertical structure and the effect of eddies on the water masses. The numerous islands affect the eddy behavior as most eddies are formed in the lee of islands, propagate westward and decay when encountering shallow bathymetry. Eddies are sparse and short-lived in the tropical area north of Fiji, impacting only the top 200 meters of water. They do not appear to be able to trap and transport waters in this region. In the Coral Sea, a region of lateral shear between currents transporting waters of different origins, eddies are more numerous and energetic. They affect the water properties down to at least 500 m depth, and anticyclonic eddies trap water to approximate to 200 m, contributing to the upper thermocline waters mixing and transport. South of New Caledonia, mesoscale eddies are ubiquitous, with typical lifetimes longer than 5 months. They affect the temperature, salinity, and velocities down to approximate to 1,000 m depth, and weakly contribute to the mixing of lower thermocline waters.
Published: 2018

36. Main eddy vertical structures observed in the four major Eastern Boundary Upwelling Systems

Author: Cori Pegliasco, Rosemary Morrow, and Alexis Chaigneau
Subjects: Dynamic height, Pycnocline, Temperature salinity diagrams, mesoscale eddies, Oceanography, eddy vertical, Geophysics, Eddy, Space and Planetary Science, Geochemistry and Petrology, Anticyclone, altimetry, Eastern Boundary Upwelling Systems, Argo floats, Earth and Planetary Sciences (miscellaneous), Upwelling, structure, Altimeter, Argo, Geology
Abstract: In the four major Eastern Boundary Upwelling Systems (EBUS), mesoscale eddies are known to modulate the biological productivity and transport near-coastal seawater properties toward the offshore ocean, however little is known about their main characteristics and vertical structure. This study combines 10 years of satellite-altimetry data and Argo float profiles of temperature and salinity, and our main goals are (i) to describe the main surface characteristics of long-lived eddies formed in each EBUS and their evolution, and (ii) to depict the main vertical structure of the eddy-types that coexist in these regions. A clustering analysis of the Argo profiles surfacing within the long-lived eddies of each EBUS allows us to determine the proportion of surface and subsurface-intensified eddies in each region, and to describe their vertical structure in terms of temperature, salinity and dynamic height anomalies. In the Peru-Chile Upwelling System, 55% of the sampled anticyclonic eddies (AEs) have subsurface-intensified maximum temperature and salinity anomalies below the seasonal pycnocline, whereas 88% of the cyclonic eddies (CEs) are surface-intensified. In the California Upwelling System, only 30% of the AEs are subsurface-intensified and all of the CEs show maximum anomalies above the pycnocline. In the Canary Upwelling System, approximate to 40% of the AEs and approximate to 60% of the CEs are subsurface-intensified with maximum anomalies extending down to 800 m depth. Finally, the Benguela Upwelling System tends to generate approximate to 40-50% of weak surface-intensified eddies and approximate to 50-60% of much stronger subsurface-intensified eddies with a clear geographical distribution. The mechanisms involved in the observed eddy vertical shapes are discussed.
Published: 2015
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37. The signature of mesoscale eddies on the air‐sea turbulent heat fluxes in the South Atlantic Ocean

Author: O. T. Sato, Guilherme P. Castelão, Alexis Chaigneau, and A. B. Villas Bôas
Subjects: Atmosphere, Boundary layer, Geophysics, Eddy, Anticyclone, Turbulence, Climatology, Mesoscale meteorology, General Earth and Planetary Sciences, Satellite, Altimeter, Geology
Abstract: By collocating 10 years (1999–2009) of remotely sensed surface turbulent heat ﬂuxes withsatellite altimetry data, we investigate the impact of oceanic mesoscale eddies on the latent and sensibleheatﬂuxesintheSouthAtlanticOcean.Instronglyenergeticregions,suchastheBrazil–Malvinasconﬂuenceand the Agulhas Current Retroﬂection, eddies explain up to 20% of the total variance in the surfaceturbulent heat ﬂuxes with averaged anomalies of ± (10–20) W/m 2 .Cyclonic(anticyclonic,respectively)eddies are associated with negative (positive) heat ﬂux anomalies that tend to cool (warm) the marineatmospheric boundary layer. A composite analysis of the turbulent heat ﬂux anomalies inside the eddiesrevealsadirectrelationshipbetweeneddyamplitudeandtheintensityofsuchanomalies.Inaddition,theseanomaliesarestrongerneartheeddycenter,decayingradiallytoreachminimumvaluesoutsidetheeddies. 1. Introduction The ocean-atmosphere system is primarily turbulent. In the mesoscale band, oceanic eddies play a crucialrole in transporting heat, salt, momentum, and biogeochemical tr acersalongtheirtrajectories,signiﬁcantlyimpactingtheoceandynamicsandﬂuxes[Olson,1991;Wunsch,1999;Morrowetal.,2003].Mesoscaleeddiesare coherent rotating features with typical horizontal scales of 50–300 km and time scales ranging fromweeks to months [Cheltonetal.,2011a].Theyalsoexhibitparticularthermohalineverticalstructuresassoci-ated with strong dynamical perturbations of the density and pressure ﬁelds [Olson,1991;Chaigneau et al.,2011; Kurian et al.,2011;Zhang et al.,2013;Roullet et al., 2014]. These perturbations extend up to the seasurface,leadingtoanomaliesonseasurfaceheight,seasurfacetemperature(SST),andwindstress,amongothers[Frengeretal.,2013;Souzaetal.,2014].Asaresult,itisexpectedthateddiesimpacttheair-seaﬂuxesandtheoverlayingatmosphericcirculation[Frengeretal.,2013].The turbulent latent (LHF) and sensible (SHF) heat ﬂuxes are the primary processes by which the oceanreleases heat to the atmosphere [ Cayan, 1992]. Both the LHF and SHF can be derived from bulk formulaelinking oceanic and atmospheric parameters—such as air-speciﬁc humidity, SST, and wind speed—to theheat exchanged at the air-sea interface [Liu et al.,1979;Fairall et al.,2003;Large and Yeager, 2009]. Theanomalies caused by mesoscale eddies in some of these parameters have been recently investigated [e.g.,White and Annis, 2003; Hausmann and Czaja, 2012; Frenger et al., 2013; Souza et al., 2014; Chelton and Xie,2010]. Although there is ample evidence that oceanic mesoscale features have a signiﬁcant impact onair-seaproperties,thereisstillalackofknowledgeabouttheirsignatureonthesurfaceturbulentheatﬂuxesandtheirpotentialcontributionstothenetsurfaceheatbudget.The recent release of daily satellite-based data from the French Research Institute for Exploitation of theSea (IFREMER) [Bentamy et al., 2013] has suﬃcient resolution to estimate the LHF and SHF associatedwith mesoscale processes. The present work merges satellite altimetry sea level anomaly (SLA) data withremotely sensed surface heat ﬂuxes to investigate the impact of mesoscale ocean eddies on the LHF andSHFintheSouthAtlanticOcean(SA).The SA encompasses both quiescent areas and two regions of intense energetic variability associated withthe presence of large mesoscale eddies (Figure 1a), namely, the Agulhas Current Retroﬂection (AGR) [Olsonand Evans,1986;Goni et al.,1997]andtheBrazil-Malvinasconﬂuence(BMC)[Garzoli and Garraﬀo,1989;Olson et al., 1988]. More speciﬁcally, we aim (i) to assess the mean LHF and SHF anomalies induced bycyclonicandanticycloniceddiesintheSA,(ii)todescribethespatialvariationsoftheheatﬂuxanomaliesinVILLASBOASETAL.
Published: 2015
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38. Density dependence, prey accessibility and prey depletion by fisheries drive Peruvian seabird population dynamics

Author: Ricardo Oliveros-Ramos, Giannina Passuni, Christophe Barbraud, Arnaud Bertrand, Alexis Chaigneau, Dimitri Gutiérrez, Hervé Demarcq, Olivier Gimenez, Karine Delord, Mariano Gutiérrez Torero, Yann Tremblay, Sophie Bertrand, Marilú Bouchon, Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Institut de Recherche pour le Développement (IRD), MARine Biodiversity Exploitation and Conservation (UMR MARBEC), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD), Instituto del Mar del Peru (IMARPE), Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut National de la Recherche Agronomique (INRA)-Université Paul-Valéry - Montpellier 3 (UPVM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut de Recherche pour le Développement (IRD [France-Sud]), Facultad de Medicina, Universidad Nacional Federico Villarreal, Lima, Perú, Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-Université de La Rochelle (ULR), Centre d'études biologiques de Chizé (CEBC), Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE)-Université de Montpellier (UM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Paul-Valéry - Montpellier 3 (UM3), UMR 212 EME 'écosystèmes marins exploités' (EME), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM), Echanges Côte-Large (ECOLA), 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-Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Direccion de Investigaciones Oceanograficas, Institute of Research for Development Department - Laboratory for Studies in Geophysics and Spatial Oceanography (LEGOS), Center for Ocean Health, Service Environnement,Direction des Affaires Scientifiques et Techniques, CNIEL, Institut National de la Recherche Agronomique (INRA)-Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), and Université Paul-Valéry - Montpellier 3 (UM3)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-École pratique des hautes études (EPHE)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD [France-Sud])-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)
Subjects: 0106 biological sciences, education.field_of_study, biology, Ecology, 010604 marine biology & hydrobiology, Population size, Population, biology.organism_classification, 010603 evolutionary biology, 01 natural sciences, Predation, Fishery, 13. Climate action, Abundance (ecology), biology.animal, [SDE]Environmental Sciences, Peruvian booby, Marine ecosystem, 14. Life underwater, Seabird, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, education, Ecology, Evolution, Behavior and Systematics, ComputingMilieux_MISCELLANEOUS, Apex predator
Abstract: International audience; In marine ecosystems top predator populations are shaped by environmental factors affecting their prey abundance. Coupling top predators’ population studies with independent records of prey abundance suggests that prey fluctuations affect fecundity parameters and abundance of their predators. However, prey may be abundant but inaccessible to their predators and a major challenge is to determine the relative importance of prey accessibility in shaping seabird populations. In addition, disentangling the effects of prey abundance and accessibility from the effects of prey removal by fisheries, while accounting for density dependence, remains challenging for marine top predators. Here, we investigate how climate, population density, and the accessibility and removal of prey (the Peruvian anchovy Engraulis ringens) by fisheries influence the population dynamics of the largest sedentary seabird community(≈ 4 million individuals belonging to guanay cormorant Phalacrocorax bougainvillii, Peruvian booby Sula variegata and Peruvian pelican Pelecanus thagus) of the northern Humboldt Current System over the past half-century. Using Gompertz state–space models we found strong evidence for density dependence in abundance for the three seabird species. After accounting for density dependence, sea surface temperature, prey accessibility (defined by the depth of the upper limit of the subsurface oxygen minimum zone) and prey removal by fisheries were retained as the best predictors of annual population size across species. These factors affected seabird abundance the current year and with year lags, suggesting effects on several demographic parameters including breeding propensity and adult survival. These findings highlight the effects of prey accessibility and fishery removals on seabird populations in marine ecosystems. This will help refine management objectives of marine ecosystems in order to ensure sufficient biomass of forage fish to avoid constraining seabird population dynamics, while taking into account of the effects of environmental variability.
Published: 2017
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39. Striations and preferred eddy tracks triggered by topographic steering of the background flow in the eastern South Pacific

Author: David Donoso, Emilio Concha, François Colas, Nikolai Maximenko, Ali Belmadani, Alexis Chaigneau, Emanuele Di Lorenzo, Department of Geophysics, Universidad de Concepción - University of Concepcion [Chile], 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), Processus de couplage à Petite Echelle, Ecosystèmes et Prédateurs Supérieurs (PEPS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), 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), 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), 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)-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)), 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), International Pacific Research Center (IPRC), School of Ocean and Earth Science and Technology (SOEST), University of Hawai‘i [Mānoa] (UHM)-University of Hawai‘i [Mānoa] (UHM), School of Earth and Atmospheric Sciences [Atlanta], Georgia Institute of Technology [Atlanta], Universidad de Concepción [Chile], Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), 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 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), 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)-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), 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)-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)-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))
Subjects: 010504 meteorology & atmospheric sciences, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Oceanography, 01 natural sciences, Mesoscale eddies, Physics::Geophysics, Physics::Fluid Dynamics, Geochemistry and Petrology, Earth and Planetary Sciences (miscellaneous), 14. Life underwater, Physics::Atmospheric and Oceanic Physics, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, regional ocean model, 010505 oceanography, mesoscale eddies, satellite altimetry, Geophysics, 13. Climate action, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Climatology, Satellite altimetry, Physics::Space Physics, quasi-zonal jets, Regional ocean model, bottom topography, Background flow, Geology, eastern South Pacific
Abstract: In recent years, persistent quasi-zonal jets or striations have been ubiquitously detected in the world ocean using satellite and in situ data as well as numerical models. This study aims at determining the role of mesoscale eddies in the generation and persistence of striations off Chile in the eastern South Pacific. A 50 year climatological integration of an eddy-resolving numerical ocean model is used to assess the long-term persistence of striations. Automated eddy tracking algorithms are applied to the model outputs and altimetry data. Results reveal that striations coincide with both polarized eddy tracks and the offshore formation of new eddies in the subtropical front and coastal transition zone, without any significant decay over time that discards random eddies as a primary driver of the striations. Localized patches of vortex stretching and relative vorticity advection, alternating meridionally near the eastern edge of the subtropical front, are associated with topographic steering of the background flow in the presence of steep topography, and with baroclinically and barotropically unstable meridional flow. These sinks and sources of vorticity are suggested to generate the banded structure further west, consistently with a -plume mechanism. On the other hand, zonal/meridional eddy advection of relative vorticity and the associated Reynolds stress covariance are consistent with eddy deformation over rough topography and participate to sustain the striations in the far field. Shear instability of mean striations is proposed to feedback onto the eddy field, acting to maintain the subtropical front eddy streets and thus the striations.
Published: 2017
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40. Spatio-temporal variability of the equatorial front in the eastern tropical Pacific from remote sensing salinity data (2010–2015)

Author: Dimitri Gutiérrez, Cristhian Asto, and Alexis Chaigneau
Subjects: geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, 0211 other engineering and technologies, Front (oceanography), Zonal and meridional, 02 engineering and technology, Oceanography, 01 natural sciences, Salinity, symbols.namesake, Climatology, Archipelago, symbols, Common spatial pattern, Satellite, Surface water, Kelvin wave, Geology, 021101 geological & geomatics engineering, 0105 earth and related environmental sciences
Abstract: In the eastern Pacific, the Equatorial Front (EF) separates the relatively cold and salty Equatorial Surface Water to the South from the relatively warm and fresh Surface Tropical Water to the North. Although previous studies have succinctly described the main EF characteristics, little is known about its spatial pattern and temporal variability beyond seasonal scale. In this study, we used 5 years of remote-sensing sea surface salinity (SSS) data, acquired by SMOS in a synoptic and continuous manner, to describe the spatio-temporal variability of the haline EF (HEF). After validating the SSS satellite dataset with concomitant in situ data, we developed an algorithm based on maximum SSS gradients to automatically identify the HEF position on every SMOS SSS map. This algorithm applied to the 4-day resolution SMOS SSS product, allows us to investigate the spatio-temporal variability of the HEF between 2010 and 2015. Seasonally, west of the Galapagos Islands, the HEF is centered at ~2°N and shows relatively weak meridional displacements. In contrast, east of the Galapagos Archipelago, the HEF varies on average between ~4°S in spring and ~2°N in autumn. At intraseasonal scales, the HEF shows meridional fluctuations of ±1.25° around its average position. These intraseasonal fluctuations are partly related to Kelvin Waves, which was more noticeable since 2014. Over the 5-year studied period, the HEF position showed a northward trend of 0.3–0.4 latitudinal degrees per year between 2010 and 2015. However, the relatively short time series does not permit to investigate whether this low-frequency trend is due to long-term variability or interdecadal fluctuations.
Published: 2019
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41. Anatomy and evolution of a cyclonic mesoscale eddy observed in the northeastern Pacific tropical-subtropical transition zone

Author: J. A. Kurczyn, Miguel F. Lavín, Victor M. Godínez, Emilio Beier, and Alexis Chaigneau
Subjects: 010504 meteorology & atmospheric sciences, 010505 oceanography, Mesoscale meteorology, Subtropics, Oceanography, 01 natural sciences, Geophysics, Space and Planetary Science, Geochemistry and Petrology, Transition zone, Earth and Planetary Sciences (miscellaneous), Geology, 0105 earth and related environmental sciences
Published: 2013
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42. Near-coastal circulation in the Northern Humboldt Current System from shipboard ADCP data

Author: Luis Vásquez, Noel Dominguez, Gérard Eldin, Vincent Echevin, Carmen Grados, Alexis Chaigneau, and Roberto Flores
Subjects: Mass transport, geography, geography.geographical_feature_category, 010504 meteorology & atmospheric sciences, 010505 oceanography, Continental shelf, Oceanography, 01 natural sciences, Current (stream), Sverdrup balance, Geophysics, Circulation (fluid dynamics), Acoustic Doppler current profiler, 13. Climate action, Space and Planetary Science, Geochemistry and Petrology, Potential vorticity, Downwelling, Earth and Planetary Sciences (miscellaneous), 14. Life underwater, Geology, 0105 earth and related environmental sciences
Abstract: The near-coastal circulation of the Northern Humboldt Current System is described analyzing ∼8700 velocity profiles acquired by a shipboard acoustic Doppler current profiler (SADCP) during 21 surveys realized between 2008 and 2012 along the Peruvian coast. This data set permits observation of (i) part of the Peru Coastal Current and the Peru Oceanic Current that flow equatorward in near-surface layers close to the coast and farther than ∼150 km from the coast, respectively; (ii) the Peru-Chile Undercurrent (PCUC) flowing poleward in subsurface layers along the outer continental shelf and inner slope; (iii) the near-surfacing Equatorial Undercurrent renamed as Ecuador-Peru Coastal Current that feeds the PCUC; and (iv) a deep equatorward current, referred to as the Chile-Peru Deep Coastal Current, flowing below the PCUC. A focus in the PCUC core layer shows that this current exhibits typical velocities of 5-10 cm s−1. The PCUC deepens with an increasing thickness poleward, consistent with the alongshore conservation of potential vorticity. The PCUC mass transport increases from ∼1.8 Sv at 5°S to a maximum value of ∼5.2 Sv at 15°S, partly explained by the Sverdrup balance. The PCUC experiences relatively weak seasonal variability and the confluence of eddy-like structures and coastal currents strongly complicates the circulation. The PCUC intensity is also affected by the southward propagation of coastally trapped waves, as revealed by a strong PCUC intensification in March 2010 coincident with the passage of a downwelling coastal wave associated with a weak El Nino event.
Published: 2013
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43. An Index to Distinguish Surface- and Subsurface-Intensified Vortices from Surface Observations

Author: Sara Fleury, Charefeddine Assassi, Rosemary Morrow, Yves Morel, R. Cambra, Cori Pegliasco, Xavier Carton, Patrice Klein, Frederic Vandermeirsch, Alexis Chaigneau, François Colas, 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 Physique et Spatiale (LOPS), 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), Space Technology Center [0ran], Agence Spatiale Algérienne = Algerian Space Agency (ASAL), Océan du Large et Variabilité Climatique (OLVAC), 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), Processus de couplage à Petite Echelle, Ecosystèmes et Prédateurs Supérieurs (PEPS), 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)-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)), 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), EPIGRAM, funded by CNRS (LEFE/IMAGO), ANR-08-BLAN-0330-01, 'Merging of satellite and in- situ observations for the analysis of meso and submesoscale dynamics,' funded by CNES (OSTST project), ANR-11-MONU-005-03 comodo, ANR-08-BLAN-0330,EPIGRAM,Etudes Physiques Intégrées en Gascogne et Région Atlantique-Manche(2008), ANR-11-MONU-0005,COMODO,Communauté de Modélisation Océanographique(2011), Centre National de la Recherche Scientifique (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)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS), Université Fédérale Toulouse Midi-Pyrénées-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), 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)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-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), 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), 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), 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)-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)-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))
Subjects: Surface (mathematics), Physical Meteorology and Climatology, 010504 meteorology & atmospheric sciences, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], subsurface, Oceanography, Atmospheric sciences, 01 natural sciences, Physics::Geophysics, Potential vorticity, Circulation/ Dynamics, Sea level, Mesoscale processes, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], Atm/Ocean Structure/ Phenomena, 010505 oceanography, Anomaly (natural sciences), vortices, sea surface density and sea surface temperature, Geophysics, Sea-surface height, sea surface height, Vortex, Sea surface temperature, Eddy, 13. Climate action, Upwelling, Geology, Eddies
Abstract: In this study, the authors first show that it is difficult to reconstruct the vertical structure of vortices using only surface observations. In particular, they show that the recent surface quasigeostrophy (SQG) and interior and surface quasigeostrophy (ISQG) methods systematically lead to surface-intensified vortices, and those subsurface-intensified vortices are thus not correctly modeled. The authors then investigate the possibility of distinguishing between surface- and subsurface-intensified eddies from surface data only, using the sea surface height and the sea surface temperature available from satellite observations. A simple index, based on the ratio of the sea surface temperature anomaly and the sea level anomaly, is proposed. While the index is expected to give perfect results for isolated vortices, the authors show that in a complex environment, errors can be expected, in particular when strong currents exist in the vicinity of the vortex. The validity of the index is then analyzed using results from a realistic regional circulation model of the Peru–Chile upwelling system, where both surface and subsurface eddies coexist. The authors find that errors are mostly associated with double-core eddies (aligned surface and subsurface cores) and that the index can be useful to determine the nature of mesoscale eddies (surface or subsurface intensified) from surface (satellite) observations. However, the errors reach 24%, and some possible improvements of the index calculations are discussed.
Published: 2016
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44. Spatial and seasonal patterns of fine-scale to mesoscale upper ocean dynamics in an Eastern Boundary Current System

Author: Gary Vargas, Daniel Grados, Dimitri Gutiérrez, François Colas, Arnaud Bertrand, Vincent Echevin, Ronan Fablet, Alexis Chaigneau, UMR 212 EME 'écosystèmes marins exploités' (EME), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM), Processus de couplage à Petite Echelle, Ecosystèmes et Prédateurs Supérieurs (PEPS), 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)-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)), 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), 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), Instituto del Mar del Peru (IMARPE), Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), Institut Mines-Télécom [Paris] (IMT)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL), 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), 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), 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)-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)), 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), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique (IMT Atlantique), and Institut Mines-Télécom [Paris] (IMT)
Subjects: Pycnocline, Isopycnal, 010504 meteorology & atmospheric sciences, 010505 oceanography, [SDE.MCG]Environmental Sciences/Global Changes, Mesoscale meteorology, Stratification (water), Climate change, Geology, Aquatic Science, Internal wave, PACIFIQUE, PEROU, 01 natural sciences, Boundary current, Ocean dynamics, Oceanography, 13. Climate action, Climatology, 14. Life underwater, 0105 earth and related environmental sciences
Abstract: International audience; The physical forcing of the ocean surface includes a variety of energetic processes, ranging from internal wave (IW) to submesoscale and mesoscale, associated with characteristic horizontal scales. While the description of mesoscale ocean dynamics has greatly benefited from the availability of satellite data, observations of finer scale patterns remain scarce. Recent studies showed that the vertical displacements of the oxycline depth, which separates the well-mixed oxygenated surface layer from the less oxygenated deeper ocean, estimated by acoustics, provide a robust proxy of isopycnal displacements over a wide range of horizontal scales. Using a high-resolution and wide-range acoustic data set in the Northern Humboldt Current System (NHCS) off Peru, the spatial and temporal patterns of fine-scale-tomesoscale upper ocean dynamics are investigated. The spectral content of oxycline/pycnocline profiles presents patterns characteristic of turbulent flows, from the mesoscale to the fine scale, and an energization at the IW scale (2 km-200 m). On the basis of a typology performed on 35,000 structures we characterized six classes of physical structures according to their shape and scale range. The analysis reveals the existence of distinct features for the fine-scale range below similar to 2-3 km, and clearly indicates the existence of intense IW and submesoscale activity over the entire NHCS region. Structures at scales smaller than 2 km were more numerous and energetic in spring than in summer. Their spatiotemporal variability supports the interpretation that these processes likely relate to IW generation by interactions between tidal flows, stratification and the continental slope. Given the impact of the physical forcing on the biogeochemical and ecological dynamics in EBUS, these processes should be further considered in future ecosystem studies based on observations and models. The intensification of upper ocean stratification resulting from climate change makes such high-resolution analyses even more critical.
Published: 2016
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45. Seasonality in marine ecosystems: Peruvian seabirds, anchovy and oceanographic conditions

Author: Sophie Bertrand, Jose Torres-Maita, Ramiro Castillo, Alexis Chaigneau, Julio Mori, Hervé Demarcq, Christophe Barbraud, Giannina Passuni, Vincent A. Viblanc, Jesus Ledesma, Arnaud Bertrand, Angel Perea, UMR 212 EME 'écosystèmes marins exploités' (EME), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM), Instituto del Mar del Peru (IMARPE), Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), 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), Département Ecologie, Physiologie et Ethologie (DEPE-IPHC), Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Centre d’Ecologie Fonctionnelle et Evolutive (CEFE), Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-École pratique des hautes études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Institut National de la Recherche Agronomique (INRA)-Université Paul-Valéry - Montpellier 3 (UPVM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut de Recherche pour le Développement (IRD [France-Sud]), Institut National de la Recherche Agronomique (INRA)-Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD [France-Sud])-Centre National de la Recherche Scientifique (CNRS)-École pratique des hautes études (EPHE)-Université de Montpellier (UM)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro)-Institut National de la Recherche Agronomique (INRA)-Centre international d'études supérieures en sciences agronomiques (Montpellier SupAgro)-Université Paul-Valéry - Montpellier 3 (UM3), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Institut National de la Recherche Agronomique (INRA)-Université de La Rochelle (ULR)
Subjects: System, 0106 biological sciences, Time Factors, Northern Humboldt Current, Oceans and Seas, Peruvian Booby, 010603 evolutionary biology, 01 natural sciences, Predation, Birds, anchovy, Abundance (ecology), biology.animal, Anchovy, prey abundance, Peru, Northern Humboldt Current System, Animals, Peruvian booby, Marine ecosystem, Ecosystem, 14. Life underwater, Phalacrocorax bougainvillii, Ecology, Evolution, Behavior and Systematics, occupancy model, Sula variegata, seasonal breeding, biology, Ecology, Reproduction, 010604 marine biology & hydrobiology, Fishes, Engraulis ringens, biology.organism_classification, Fishery, Pelican, oceanographic variability, Predatory Behavior, Pelecanus thagus, [SDE]Environmental Sciences, Seasons, Seabird, Guanay Cormorant, Peruvian Pelican
Abstract: International audience; In fl uctuating environments, matching breeding timing to periods of highresource availability is crucial for the fi tness of many vertebrate species, and may havemajor consequences on population health. Yet, our understanding of the proximate environmentalcues driving seasonal breeding is limited. This is particularly the case in marineecosystems, where key environmental factors and prey abundance and availability areseldom quantifi ed. The Northern Humboldt Current System ( NHCS ) is a highly productive,low- latitude ecosystem of moderate seasonality. In this ecosystem, three tropical seabirdspecies (the Guanay Cormorant Phalacrocorax bougainvillii , the Peruvian Booby Sula variegata ,and the Peruvian Pelican Pelecanus thagus ) live in sympatry and prey almost exclusivelyon anchovy, Engraulis ringens . From January 2003 to December 2012, we monitored 31breeding sites along the Peruvian coast to investigate the breeding cycle of these species.We tested for relationships between breeding timing, oceanographic conditions, and preyavailability using occupancy models. We found that all three seabird species exhibitedseasonal breeding patterns, with marked interspecifi c differences. Whereas breeding mainlystarted during the austral winter/early spring and ended in summer/early fall, this patternwas stronger in boobies and pelicans than in cormorants. Breeding onset mainly occurredwhen upwelling was intense but ecosystem productivity was below its annual maxima, andwhen anchovy were less available and in poor physiological condition. Conversely, theabundance and availability of anchovy improved during chick rearing and peaked aroundthe time of fl edging. These results suggest that breeding timing is adjusted so that fl edgingmay occur under optimal environmental conditions, rather than being constrained by nutritionalrequirements during egg laying. Adjusting breeding time so that fl edglings meetoptimal conditions at independence is unique compared with other upwelling ecosystemsand could be explained by the relatively high abundances of anchovy occurring throughoutthe year in the NHCS .
Published: 2016
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46. Biological characteristics of the hydrological landscapes in the Bay of Biscay in spring 2009

Author: Xabier Irigoien, Daniel Grados, Alexis Chaigneau, Anne Lebourges-Dhaussy, Ainhoa Lezama-Ochoa, Arnaud Bertrand, AZTI - Tecnalia, Instituto del Mar del Peru (IMARPE), Laboratoire des Sciences de l'Environnement Marin (LEMAR) (LEMAR), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Institut Universitaire Européen de la Mer (IUEM), Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD), 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), MARine Biodiversity Exploitation and Conservation (UMR MARBEC), and Centre National de la Recherche Scientifique (CNRS)-Université de Montpellier (UM)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut de Recherche pour le Développement (IRD)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, Biogeography, [SDE.MCG]Environmental Sciences/Global Changes, Aquatic Science, Oceanography, 01 natural sciences, Predation, hydrological structures, [SDV.EE.ECO]Life Sciences [q-bio]/Ecology, environment/Ecosystems, Spring (hydrology), patterns, 14. Life underwater, acoustics, biogeography, 0105 earth and related environmental sciences, fish, geography, Biomass (ecology), geography.geographical_feature_category, 010604 marine biology & hydrobiology, ACL, 15. Life on land, Light attenuation, Bay of Biscay, macrozooplankton, 13. Climate action, %22">Fish , Environmental science, Thermohaline circulation, horizontal distribution, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, Bay
Abstract: International audience; In the present study we investigated the biogeography of macrozooplankton and fish biomass in the Bay of Biscay. In this region, we defined six different landscapes based on the hydrogeographical characteristics observed in spring 2009. We then related landscape's characteristics and environmental parameters such as light attenuation depth and chlorophyll-a with macrozooplankton and fish acoustic biomass. Hydrodynamic structures together with coastal influences (river discharges, predation pressure and depth preference) and vertical thermohaline structure/mixing (feeding modes and ability to stay in preferred layers) appeared as the main factors determining the biological distribution. Besides, variance partitioning was used to assess the respective roles played by the hydrological environment, the geographical space and the biological environment alone, and their interactions. Results revealed that: (i) macrozooplankton and fish have a preference for different hydrogeographical landscapes; (ii) the association between hydrological conditions and geographical features, i.e. the spatial structure of the hydrological environment, plays a key role in the distribution of macrozooplankton; and (iii) prey-predator relationships have to be taken into account to provide a comprehensive characterization of habitat suitability.
Published: 2015
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47. Cold-core anomalies at the subantarctic front, south of Tasmania

Author: Jean-Rene Donguy, Rosemary Morrow, Stephen R. Rintoul, Alexis Chaigneau, Océan du Large et Variabilité Climatique (OLVAC), 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), Commonwealth Scientific and Industrial Research Organisation (CSIRO) (CSIRO), and Commonwealth Scientific and Industrial Research Organisation (CSIRO)
Subjects: Subpolar zone, SALINITE, cooling, 010504 meteorology & atmospheric sciences, Subantarctic Mode Water, Summer, bathymetry, sea level, Aquatic Science, Oceanography, 01 natural sciences, salinity, ALTIMETRIE, Cold low, VARIATION TEMPORELLE, altimetry, ANOMALIE DE TEMPERATURE, Ekman transport, Bathymetry, 14. Life underwater, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, Sea level, Vertical propagation, 0105 earth and related environmental sciences, TEMPERATURE DE SURFACE, Propagation characteristic, Australasia, DONNEES SATELLITE, 010505 oceanography, Australia, Front (oceanography), Surface temperature, Eddy, 13. Climate action, Climatology, NIVEAU MARIN, VARIATION SPATIALE, Meander, anomalies, meanders, Tasmania Australia, Hydrography, Geology
Abstract: International audience; Eight years of altimetry and hydrographic data are used to examine the formation, propagation and vertical characteristics of cold-core rings formed north of the Subantarctic Front, SAF, in the region south of Tasmania. Altimetry allows us to follow the spatial-temporal evolution of these cold, low sea level anomalies. Most of these cold-core rings are formed from unstable meanders of the SAF, and the interaction of the meanders with bathymetry appears to influence the eddy spawning. The interaction of a westward propagating cold-core eddy with an eastward propagating equatorward meander can also trigger a cold-core eddy spawning event. Hydrographic sections show that these eddies have cool, low-salinity cores reaching to at least 1500 m depth. During summer, their surface temperature signal is eliminated only 2-3 weeks after spawning, however, their surface salinity signature is maintained for 2-3 months. We estimate that these cold-core eddies could contribute an annual heat deficit of -3.8 x 1019 J, and an annual salt deficit of -1.6 x 1012 kg, and contribute to cooling and freshening the region north of the SAF where mode waters form. The salt deficit is equivalent to that introduced by the northward Ekman transport, suggesting that eddies may play an important role in transporting low-salinity water into the Subantarctic Zone.
Published: 2004
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48. Seasonal and interannual variations of the upper ocean energetics between Tasmania and Antarctica

Author: Rosemary Morrow, Aurore Brut, Alexis Chaigneau, Océan du Large et Variabilité Climatique (OLVAC), 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), Centre d'études spatiales de la biosphère (CESBIO), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-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), and Echanges Côte-Large (ECOLA)
Subjects: VARIATION SAISONNIERE, 010504 meteorology & atmospheric sciences, Aquatic Science, Oceanography, Spatial distribution, 01 natural sciences, ALTIMETRIE, Physics::Geophysics, Physics::Fluid Dynamics, ANOMALIE DE TEMPERATURE, Bathymetry, 14. Life underwater, [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography, FLUX THERMIQUE, Physics::Atmospheric and Oceanic Physics, 0105 earth and related environmental sciences, Line (formation), DONNEES SATELLITE, XBT, 010505 oceanography, Energetics, VARIATION INTERANNUELLE, Current (stream), Heat flux, 13. Climate action, Climatology, COURANT MARIN, Ocean heat content, Bathythermograph, Geology
Abstract: International audience; Nine years of Topex/Poseidon and ERS satellite altimetry and XBT data from the SURVOSTRAL program were used to analyze the seasonal and interannual variations of the eddy energetics in terms of its spatial distribution and relation with the upper ocean heat content. Eddy kinetic energy is calculated in two frequency bands one associated with transient and the other with low-frequency variability. The two eddy components have distinct geographical distribution. At the SURVOSTRAL line, the transient eddy energy is twice the low-frequency energy, with maximum transient energy occurring during the austral summer period and maximum low-frequency energy in winter. The site is one of growing eddy energy. Eddy momentum flux is northward over the SURVOSTRAL line, and the summertime eddy heat flux is poleward across the Subantarctic and Subtropical Fronts, and equatorward either side of the fronts. Eddy fluxes are strongly influenced by their position relative to the bathymetry and the mean current.
Published: 2003
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49. Ecosystem scenarios shape fishermen spatial behavior. The case of the Peruvian anchovy fishery in the Northern Humboldt Current system

Author: Marilú Bouchon, Jorge Tam, Marceliano Segura, Arnaud Bertrand, Monique Simier, Dimitri Gutiérrez, Rocio Joo, Hervé Demarcq, Ronan Fablet, Sophie Bertrand, Alexis Chaigneau, Mariano Gutiérrez, UMR 212 EME 'écosystèmes marins exploités' (EME), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM), Instituto del Mar del Peru (IMARPE), 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), Universidad National Federico Villareal (UNFV), Lab-STICC_TB_CID_TOMS, Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), Département Signal et Communications (SC), Institut Mines-Télécom [Paris] (IMT)-Télécom Bretagne-Université européenne de Bretagne - European University of Brittany (UEB), 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 européenne de Bretagne - European University of Brittany (UEB)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), and Université européenne de Bretagne - European University of Brittany (UEB)-Télécom Bretagne-Institut Mines-Télécom [Paris] (IMT)
Subjects: VARIATION SAISONNIERE, Fishing, FONCTIONNEMENT DE L'ECOSYSTEME, PECHEUR, Aquatic Science, Spatial distribution, Marine ecology, POISSON MARIN, Vessel monitoring system, Anchovy, Ecosystem, 14. Life underwater, Apex predator, Trophic level, Biomass (ecology), biology, PECHE COTIERE, FACTEUR ECOLOGIQUE, Geology, COMPORTEMENT, biology.organism_classification, MODELISATION, Fishery, Oceanography, 13. Climate action, INDICATEUR ECOLOGIQUE, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, VARIATION PLURIANNUELLE, RELATION PREDATEUR PROIE
Abstract: A major goal in marine ecology is the understanding of the interactions between the dynamics of the different ecosystem components, from physics to top predators. While fishermen are among the main top predators at sea, almost none of the existing studies on ecology from physics to top predators contemplate fishermen as part of the system. The present work focuses on the coastal processes in the Northern Humboldt Current System, which encompasses both an intense climatic variability and the largest mono-specific fishery of the world. From concomitant satellite, acoustic survey and Vessel Monitoring System data (similar to 90,000 fishing trips) for a ten-year period (2000-2009), we quantify the associations between the dynamics of the spatial behavior of fishermen, environmental conditions and anchovy (Engraulis ringens) biomass and spatial distribution. Using multivariate statistical analyses we show that environmental and anchovy conditions do significantly shape fishermen spatial behavior and present evidences that environmental fluctuations smoothed out along trophic levels. We propose a retrospective analysis of the study period in the light of the ecosystem scenarios evidenced and we finally discuss the potential use of fishermen spatial behavior as ecosystem indicator. (C) 2014 Elsevier Ltd. All rights reserved.
Published: 2014
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50. Broad impacts of fine-scale dynamics on seascape structure from zooplankton to seabirds

Author: Daniel Grados, Alexis Chaigneau, Sophie Bertrand, François Colas, Gary Vargas, Arnaud Bertrand, Alexandre Mousseigne, Xavier Capet, Ronan Fablet, UMR 212 EME 'écosystèmes marins exploités' (EME), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM), Instituto del Mar del Peru (IMARPE), Processus de couplage à Petite Echelle, Ecosystèmes et Prédateurs Supérieurs (PEPS), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), 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), 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), 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)-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)), 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), 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), Lab-STICC_TB_CID_TOMS, Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance (Lab-STICC), Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), 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)-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)), 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), École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-Télécom Bretagne-Institut Brestois du Numérique et des Mathématiques (IBNM), Université de Brest (UBO)-Université européenne de Bretagne - European University of Brittany (UEB)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), Département Signal et Communications (IMT Atlantique - SC), IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Lab-STICC_IMTA_CID_TOMS, École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-École Nationale d'Ingénieurs de Brest (ENIB)-Université de Bretagne Sud (UBS)-Université de Brest (UBO)-École Nationale Supérieure de Techniques Avancées Bretagne (ENSTA Bretagne)-Institut Mines-Télécom [Paris] (IMT)-Centre National de la Recherche Scientifique (CNRS)-Université Bretagne Loire (UBL)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), and Institut Mines-Télécom [Paris] (IMT)
Subjects: 0106 biological sciences, 010504 meteorology & atmospheric sciences, General Physics and Astronomy, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], 01 natural sciences, Zooplankton, Article, General Biochemistry, Genetics and Molecular Biology, Birds, [INFO.INFO-TS]Computer Science [cs]/Signal and Image Processing, Water Movements, Animals, Seawater, Ecosystem, Marine ecosystem, 14. Life underwater, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Trophic level, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, Seascape, Multidisciplinary, Ecology, 010604 marine biology & hydrobiology, Ecological dynamics, General Chemistry, Sound, Oceanography, 13. Climate action, Environmental science, Scale (map)
Abstract: In marine ecosystems, like most natural systems, patchiness is the rule. A characteristic of pelagic ecosystems is that their ‘substrate’ consists of constantly moving water masses, where ocean surface turbulence creates ephemeral oases. Identifying where and when hotspots occur and how predators manage those vagaries in their preyscape is challenging because wide-ranging observations are lacking. Here we use a unique data set, gathering high-resolution and wide-range acoustic and GPS-tracking data. We show that the upper ocean dynamics at scales less than 10 km play the foremost role in shaping the seascape from zooplankton to seabirds. Short internal waves (100 m–1 km) play a major role, while submesoscale (~1–20 km) and mesoscale (~20–100 km) turbulence have a comparatively modest effect. Predicted changes in surface stratification due to global change are expected to have an impact on the number and intensity of physical structures and thus biological interactions from plankton to top predators., Ocean circulations can strongly influence ecological dynamics in marine ecosystem over multiple spatial scales. Here, Bertrand et al. find that the majority of these interactions occur within small-scale hotspots that concentrate interactions across many trophic levels from zooplankton to seabirds.
Published: 2014
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