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90 Research products, page 1 of 9

  • European Marine Science
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  • 2013-2022
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  • Open Access
    Authors: 
    Hingamp P.; Iudicone D.; Brum J. R.; Zingone A.; Wincker P.; -P, Gattuso J.; Guidi L.; Sullivan M. B.; Casotti R.; de Vargas C.; +43 more
    Publisher: American Association for the Advancement of Science (AAAS)
    Project: TARA | Tara Oceans (2)

    Agulhas rings provide the principal route for ocean waters to circulate from the Indo-Pacific to the Atlantic basin. Their influence on global ocean circulation is well known, but their role in plankton transport is largely unexplored. We show that, although the coarse taxonomic structure of plankton communities is continuous across the Agulhas choke point, South Atlantic plankton diversity is altered compared with Indian Ocean source populations. Modeling and in situ sampling of a young Agulhas ring indicate that strong vertical mixing drives complex nitrogen cycling, shaping community metabolism and biogeochemical signatures as the ring and associated plankton transit westward. The peculiar local environment inside Agulhas rings may provide a selective mechanism contributing to the limited dispersal of Indian Ocean plankton populations into the Atlantic.

  • Open Access English
    Authors: 
    Michaud, H.; Marsaleix, P.; Leredde, Y.; Estournel, C.; Bourrin, F.; Lyard, F.; Mayet, C.; Ardhuin, F.;
    Project: EC | IOWAGA (240009)

    We develop and implement a new method to take into account the impact of waves into the 3-D circulation model SYMPHONIE (Marsaleix et al., 2008, 2009a) following the simplified equations of Bennis et al. (2011) which use glm2z-RANS theory (Ardhuin et al., 2008c). These adiabatic equations are completed by additional parameterizations of wave breaking, bottom friction and wave-enhanced vertical mixing, making the forcing valid from the surf zone through to the open ocean. The wave forcing is performed by wave generation and propagation models WAVEWATCH III® (Tolman, 2008, 2009; Ardhuin et al., 2010) and SWAN (Booij et al., 1999). The model is tested and compared with other models for a plane beach test case, previously tested by Haas and Warner (2009)and Uchiyama et al. (2010). A comparison is also made with the laboratory measurements of Haller et al. (2002) of a barred beach with channels. Results fit with previous simulations performed by other models and with available observational data. Finally, a realistic case is simulated with energetic waves travelling over a coast of the Gulf of Lion (in the northwest of the Mediterranean Sea) for which currents are available at different depths as well as an accurate bathymetric database of the 0–10 m depth range. A grid nesting approach is used to account for the different forcings acting at different spatial scales. The simulation coupling the effects of waves and currents is successful to reproduce the powerful northward littoral drift in the 0–15 m depth zone. More precisely, two distinct cases are identified: When waves have a normal angle of incidence with the coast, they are responsible for complex circulation cells and rip currents in the surf zone, and when they travel obliquely, they generate a northward littoral drift. These features are more complicated than in the test cases, due to the complex bathymetry and the consideration of wind and non-stationary processes. Wave impacts in the inner shelf are less visible since wind and regional circulation seem to be the predominant forcings. Besides, a discrepancy between model and observations is noted at that scale, possibly linked to an underestimation of the wind stress. This three-dimensional method allows a good representation of vertical current profiles and permits the calculation of the shear stress associated with waves and currents. Future work will focus on the combination with a sediment transport model.

  • Open Access English
    Authors: 
    LACROIX, Denis; DAVID, Bernard; LAMBLIN, Véronique; DE MENTHIERE, Nicolas; DE LATTRE-GASQUET, Marie; GUIGON, Antoine; JANNES-OBER, Emmanuelle; HERVIEU, Halvard; POTIER, Françoise; RAGAIN, Gilles; +1 more
    Country: France

    The perception of ocean areas by policy-makers or by people, living or not on the coast, has significantly varied over centuries. Due to its vastness and complexity, the sea has been studied within distinct academic disciplines. However, the current issues related to the sea, such as climate change, marine pollution or coastal tourism, require an integrated vision of the assets and drawbacks in order to meet the challenges arising from human activities both at sea and onshore. In this study, a group of foresight officers from the French network of public research institutes decided to cross-check and compare several science approaches (biology, sociology, economics, etc) about oceans. Thus, 11 sectors of maritime activity (transportation, fisheries, energy, etc.) were cross-tabulated with 9 basic social functions (providing food, housing, learning, etc.). In this matrix, the main challenges and issues projected for 2030 were sought, in the frame of a baseline scenario. Results were clustered through 4 criteria, leading to 9 major challenges, each of them broken down into two important issues for research. The outcomes were used to create a survey, allowing the ranking of the research priorities. Most of the 9 challenges tally with the research and development objectives of great maritime states, except for governance and monitoring, which remain underscored. As a result, maritime powers still show more interest on securing national resources rather than on promoting international cooperation for secure trade and sustainable exploitation of marine resources. But foresight in this field could help changing the mentalities notably because oceans show clearly now to be a vital common good for mankind.

  • Open Access English
    Authors: 
    Waelbroeck, Claire; Pichat, Sylvain; Böhm, Evelyn; Lougheed, Bryan C.; Faranda, Davide; Vrac, Mathieu; Missiaen, Lise; Vazquez Riveiros, Natalia; Burckel, Pierre; Lippold, Jörg; +4 more
    Project: ANR | RETRO (ANR-09-BLAN-0347), EC | ACCLIMATE (339108)

    Thanks to its optimal location on the northern Brazilian margin, core MD09-3257 records both ocean circulation and atmospheric changes. The latter occur locally in the form of increased rainfall on the adjacent continent during the cold intervals recorded in Greenland ice and northern North Atlantic sediment cores (i.e., Greenland stadials). These rainfall events are recorded in MD09-3257 as peaks in ln(Ti ∕ Ca). New sedimentary Pa ∕ Th data indicate that mid-depth western equatorial water mass transport decreased during all of the Greenland stadials of the last 40 kyr. Using cross-wavelet transforms and spectrogram analysis, we assess the relative phase between the MD09-3257 sedimentary Pa ∕ Th and ln(Ti ∕ Ca) signals. We show that decreased water mass transport between a depth of ∼1300 and 2300 m in the western equatorial Atlantic preceded increased rainfall over the adjacent continent by 120 to 400 yr at Dansgaard–Oeschger (D–O) frequencies, and by 280 to 980 yr at Heinrich-like frequencies. We suggest that the large lead of ocean circulation changes with respect to changes in tropical South American precipitation at Heinrich-like frequencies is related to the effect of a positive feedback involving iceberg discharges in the North Atlantic. In contrast, the absence of widespread ice rafted detrital layers in North Atlantic cores during D–O stadials supports the hypothesis that a feedback such as this was not triggered in the case of D–O stadials, with circulation slowdowns and subsequent changes remaining more limited during D–O stadials than Heinrich stadials.

  • Open Access English
    Authors: 
    AULANIER, Florian; NICOLAS, Barbara; ROUX, Philippe; MARS, Jerome;
    Publisher: ACOUSTICAL SOCIETY OF AMERICA
    Country: France

    Broadband acoustic signals around 1 kHz propagate through shallow water oceanic waveguides of ~100 m in depth and ~2 km in range as multiple ray-like wavefronts. These acoustic arrivals can be characterized by the following observables: travel-time (TT), direction-of-arrival (DOA) and direction-of-departure (DOD). By applying double-beamforming on the point-to-point signals recorded between two source-receiver arrays, the acoustic contribution of each arrival can be separated from the multi-reverberated data and the TT, DOA and DOD observable variations are accurately measured. This study deals with the use of time-angle sensitivity kernels (TASK) to estimate the observable variations induced by sound speed perturbations in the waveguide. This approach is based on the first order Born approximation and takes into account the finite-frequency effects associated with wave propagation. The robustness the TASK approach is analyzed and compared to numerical parabolic equation simulations involving different sound speed perturbations. For example, parameters such as the perturbation location, the value and shape of the perturbation in the waveguide are modified. The combination of several perturbations and the influence of the source-receiver array apertures on the TT, DOA and DOD estimates are also studied.

  • Open Access English
    Authors: 
    Ye, Y.; Wagener, T.; Völker, C.; Guieu, C.; Wolf-Gladrow, D. A.;
    Project: EC | DAPOP (236694), ANR | DUNE (ANR-07-BLAN-0126)

    A significant decrease of dissolved iron (DFe) concentration has been observed after dust addition into mesocosms during the DUst experiment in a low Nutrient low chlorophyll Ecosystem (DUNE), carried out in the summer of 2008. Due to low biological productivity at the experiment site, biological consumption of iron can not explain the magnitude of DFe decrease. To understand processes regulating the observed DFe variation, we simulated the experiment using a one-dimensional model of the Fe biogeochemical cycle, coupled with a simple ecosystem model. Different size classes of particles and particle aggregation are taken into account to describe the particle dynamics. DFe concentration is regulated in the model by dissolution from dust particles and adsorption onto particle surfaces, biological uptake, and photochemical mobilisation of particulate iron. The model reproduces the observed DFe decrease after dust addition well. This is essentially explained by particle adsorption and particle aggregation that produces a high export within the first 24 h. The estimated particle adsorption rates range between the measured adsorption rates of soluble iron and those of colloidal iron, indicating both processes controlling the DFe removal during the experiment. A dissolution timescale of 3 days is used in the model, instead of an instantaneous dissolution, underlining the importance of dissolution kinetics on the short-term impact of dust deposition on seawater DFe. Sensitivity studies reveal that initial DFe concentration before dust addition was crucial for the net impact of dust addition on DFe during the DUNE experiment. Based on the balance between abiotic sinks and sources of DFe, a critical DFe concentration has been defined, above which dust deposition acts as a net sink of DFe, rather than a source. Taking into account the role of excess iron binding ligands and biotic processes, the critical DFe concentration might be applied to explain the short-term variability of DFe after natural dust deposition in various different ocean regions.

  • Open Access English
    Authors: 
    Burckel, Pierre; Waelbroeck, Claire; Luo, Yiming; Roche, Didier M; Pichat, Sylvain; Jaccard, Samuel L; Gherardi, Jeanne-Marie; Govin, Aline; Lippold, Jörg; Thil, François;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | ACCLIMATE (339108), SNSF | SeaO2 - Past changes in S... (144811), ANR | RETRO (ANR-09-BLAN-0347), SNSF | Quantifying changes in th... (111588)

    We reconstruct the geometry and strength of the Atlantic Meridional Overturning Circulation during Heinrich Stadial 2 and three Greenland interstadials of the 20-50 ka period based on the comparison of new and published sedimentary 231Pa/230Th data with simulated sedimentary 231Pa/230Th. We show that the deep Atlantic circulation during these interstadials was very different from that of the Holocene. Northern-sourced waters likely circulated above 2500 m depth, with a flow rate lower than that of the present day North Atlantic Deep Water (NADW). Southern-sourced deep waters most probably flowed northwards below 4000 m depth into the North Atlantic basin, and then southwards as a return flow between 2500 and 4000 m depth. The flow rate of this southern-sourced deep water was likely larger than that of the modern Antarctic Bottom Water (AABW). Our results further show that during Heinrich Stadial 2, the deep Atlantic was probably directly affected by a southern-sourced water mass below 2500 m depth, while a slow southward flowing water mass originating from the North Atlantic likely influenced depths between 1500 and 2500 m down to the equator.

  • Other research product . Other ORP type . 2015
    Open Access
    Authors: 
    de Vargas, Colomban; Probert, Ian; Carmichael, Margaux; Poulain, Julie; Romac, Sarah; Colin, Sébastien; Aury, Jean-Marc; Bittner, Lucie; Chaffron, Samuel; Dunthorn, Micah; +45 more
    Project: TARA | Tara Oceans (2)

    Accompanying material, text, data and figures for the article de Vargas et al., 'Eukaryotic plankton diversity in the sunlit ocean', Science 348, 1261605 (2015), doi: 10.1126/science.1261605

  • Open Access English
    Authors: 
    Sourdeval, Odran; Gryspeerdt, Edward; Krämer, Martina; Goren, Tom; Delanoë, Julien; Afchine, Armin; Hemmer, Friederike; Quaas, Johannes;
    Project: EC | QUAERERE (306284), EC | MSCCC (703880)

    The number concentration of cloud particles is a key quantity for understanding aerosol–cloud interactions and describing clouds in climate and numerical weather prediction models. In contrast with recent advances for liquid clouds, few observational constraints exist regarding the ice crystal number concentration (Ni). This study investigates how combined lidar–radar measurements can be used to provide satellite estimates of Ni, using a methodology that constrains moments of a parameterized particle size distribution (PSD). The operational liDAR–raDAR (DARDAR) product serves as an existing base for this method, which focuses on ice clouds with temperatures Tc<-30 ∘C. Theoretical considerations demonstrate the capability for accurate retrievals of Ni, apart from a possible bias in the concentration in small crystals when Tc≳−50 ∘C, due to the assumption of a monomodal PSD shape in the current method. This is verified via a comparison of satellite estimates to coincident in situ measurements, which additionally demonstrates the sufficient sensitivity of lidar–radar observations to Ni. Following these results, satellite estimates of Ni are evaluated in the context of a case study and a preliminary climatological analysis based on 10 years of global data. Despite a lack of other large-scale references, this evaluation shows a reasonable physical consistency in Ni spatial distribution patterns. Notably, increases in Ni are found towards cold temperatures and, more significantly, in the presence of strong updrafts, such as those related to convective or orographic uplifts. Further evaluation and improvement of this method are necessary, although these results already constitute a first encouraging step towards large-scale observational constraints for Ni. Part 2 of this series uses this new dataset to examine the controls on Ni.

  • English
    Authors: 
    Lucken, Michael;
    Publisher: HAL CCSD
    Country: France

    Michael Lucken est un historien et historien de l’art français. Enseignant à l’Inalco depuis 1998, il est nommé en 2010 membre de l’Institut Universitaire de France. Il réalise à compter de cette date plusieurs missions en Asie de l’Est et dans le Pacifique dans le but de documenter les monuments et lieux de mémoire de la Seconde Guerre mondiale dans cette région du monde. Il est l’auteur, entre autres, de 1945-Hiroshima : les images-sources (Hermann, 2008) et Les Japonais et la guerre, 1937-1952 (Fayard, 2013).; Débris d'un bombardier japonais, en service de 1940 à 1945.

Advanced search in Research products
Research products
arrow_drop_down
Searching FieldsTerms
Any field
arrow_drop_down
includes
arrow_drop_down
Include:
The following results are related to European Marine Science. Are you interested to view more results? Visit OpenAIRE - Explore.
90 Research products, page 1 of 9
  • Open Access
    Authors: 
    Hingamp P.; Iudicone D.; Brum J. R.; Zingone A.; Wincker P.; -P, Gattuso J.; Guidi L.; Sullivan M. B.; Casotti R.; de Vargas C.; +43 more
    Publisher: American Association for the Advancement of Science (AAAS)
    Project: TARA | Tara Oceans (2)

    Agulhas rings provide the principal route for ocean waters to circulate from the Indo-Pacific to the Atlantic basin. Their influence on global ocean circulation is well known, but their role in plankton transport is largely unexplored. We show that, although the coarse taxonomic structure of plankton communities is continuous across the Agulhas choke point, South Atlantic plankton diversity is altered compared with Indian Ocean source populations. Modeling and in situ sampling of a young Agulhas ring indicate that strong vertical mixing drives complex nitrogen cycling, shaping community metabolism and biogeochemical signatures as the ring and associated plankton transit westward. The peculiar local environment inside Agulhas rings may provide a selective mechanism contributing to the limited dispersal of Indian Ocean plankton populations into the Atlantic.

  • Open Access English
    Authors: 
    Michaud, H.; Marsaleix, P.; Leredde, Y.; Estournel, C.; Bourrin, F.; Lyard, F.; Mayet, C.; Ardhuin, F.;
    Project: EC | IOWAGA (240009)

    We develop and implement a new method to take into account the impact of waves into the 3-D circulation model SYMPHONIE (Marsaleix et al., 2008, 2009a) following the simplified equations of Bennis et al. (2011) which use glm2z-RANS theory (Ardhuin et al., 2008c). These adiabatic equations are completed by additional parameterizations of wave breaking, bottom friction and wave-enhanced vertical mixing, making the forcing valid from the surf zone through to the open ocean. The wave forcing is performed by wave generation and propagation models WAVEWATCH III® (Tolman, 2008, 2009; Ardhuin et al., 2010) and SWAN (Booij et al., 1999). The model is tested and compared with other models for a plane beach test case, previously tested by Haas and Warner (2009)and Uchiyama et al. (2010). A comparison is also made with the laboratory measurements of Haller et al. (2002) of a barred beach with channels. Results fit with previous simulations performed by other models and with available observational data. Finally, a realistic case is simulated with energetic waves travelling over a coast of the Gulf of Lion (in the northwest of the Mediterranean Sea) for which currents are available at different depths as well as an accurate bathymetric database of the 0–10 m depth range. A grid nesting approach is used to account for the different forcings acting at different spatial scales. The simulation coupling the effects of waves and currents is successful to reproduce the powerful northward littoral drift in the 0–15 m depth zone. More precisely, two distinct cases are identified: When waves have a normal angle of incidence with the coast, they are responsible for complex circulation cells and rip currents in the surf zone, and when they travel obliquely, they generate a northward littoral drift. These features are more complicated than in the test cases, due to the complex bathymetry and the consideration of wind and non-stationary processes. Wave impacts in the inner shelf are less visible since wind and regional circulation seem to be the predominant forcings. Besides, a discrepancy between model and observations is noted at that scale, possibly linked to an underestimation of the wind stress. This three-dimensional method allows a good representation of vertical current profiles and permits the calculation of the shear stress associated with waves and currents. Future work will focus on the combination with a sediment transport model.

  • Open Access English
    Authors: 
    LACROIX, Denis; DAVID, Bernard; LAMBLIN, Véronique; DE MENTHIERE, Nicolas; DE LATTRE-GASQUET, Marie; GUIGON, Antoine; JANNES-OBER, Emmanuelle; HERVIEU, Halvard; POTIER, Françoise; RAGAIN, Gilles; +1 more
    Country: France

    The perception of ocean areas by policy-makers or by people, living or not on the coast, has significantly varied over centuries. Due to its vastness and complexity, the sea has been studied within distinct academic disciplines. However, the current issues related to the sea, such as climate change, marine pollution or coastal tourism, require an integrated vision of the assets and drawbacks in order to meet the challenges arising from human activities both at sea and onshore. In this study, a group of foresight officers from the French network of public research institutes decided to cross-check and compare several science approaches (biology, sociology, economics, etc) about oceans. Thus, 11 sectors of maritime activity (transportation, fisheries, energy, etc.) were cross-tabulated with 9 basic social functions (providing food, housing, learning, etc.). In this matrix, the main challenges and issues projected for 2030 were sought, in the frame of a baseline scenario. Results were clustered through 4 criteria, leading to 9 major challenges, each of them broken down into two important issues for research. The outcomes were used to create a survey, allowing the ranking of the research priorities. Most of the 9 challenges tally with the research and development objectives of great maritime states, except for governance and monitoring, which remain underscored. As a result, maritime powers still show more interest on securing national resources rather than on promoting international cooperation for secure trade and sustainable exploitation of marine resources. But foresight in this field could help changing the mentalities notably because oceans show clearly now to be a vital common good for mankind.

  • Open Access English
    Authors: 
    Waelbroeck, Claire; Pichat, Sylvain; Böhm, Evelyn; Lougheed, Bryan C.; Faranda, Davide; Vrac, Mathieu; Missiaen, Lise; Vazquez Riveiros, Natalia; Burckel, Pierre; Lippold, Jörg; +4 more
    Project: ANR | RETRO (ANR-09-BLAN-0347), EC | ACCLIMATE (339108)

    Thanks to its optimal location on the northern Brazilian margin, core MD09-3257 records both ocean circulation and atmospheric changes. The latter occur locally in the form of increased rainfall on the adjacent continent during the cold intervals recorded in Greenland ice and northern North Atlantic sediment cores (i.e., Greenland stadials). These rainfall events are recorded in MD09-3257 as peaks in ln(Ti ∕ Ca). New sedimentary Pa ∕ Th data indicate that mid-depth western equatorial water mass transport decreased during all of the Greenland stadials of the last 40 kyr. Using cross-wavelet transforms and spectrogram analysis, we assess the relative phase between the MD09-3257 sedimentary Pa ∕ Th and ln(Ti ∕ Ca) signals. We show that decreased water mass transport between a depth of ∼1300 and 2300 m in the western equatorial Atlantic preceded increased rainfall over the adjacent continent by 120 to 400 yr at Dansgaard–Oeschger (D–O) frequencies, and by 280 to 980 yr at Heinrich-like frequencies. We suggest that the large lead of ocean circulation changes with respect to changes in tropical South American precipitation at Heinrich-like frequencies is related to the effect of a positive feedback involving iceberg discharges in the North Atlantic. In contrast, the absence of widespread ice rafted detrital layers in North Atlantic cores during D–O stadials supports the hypothesis that a feedback such as this was not triggered in the case of D–O stadials, with circulation slowdowns and subsequent changes remaining more limited during D–O stadials than Heinrich stadials.

  • Open Access English
    Authors: 
    AULANIER, Florian; NICOLAS, Barbara; ROUX, Philippe; MARS, Jerome;
    Publisher: ACOUSTICAL SOCIETY OF AMERICA
    Country: France

    Broadband acoustic signals around 1 kHz propagate through shallow water oceanic waveguides of ~100 m in depth and ~2 km in range as multiple ray-like wavefronts. These acoustic arrivals can be characterized by the following observables: travel-time (TT), direction-of-arrival (DOA) and direction-of-departure (DOD). By applying double-beamforming on the point-to-point signals recorded between two source-receiver arrays, the acoustic contribution of each arrival can be separated from the multi-reverberated data and the TT, DOA and DOD observable variations are accurately measured. This study deals with the use of time-angle sensitivity kernels (TASK) to estimate the observable variations induced by sound speed perturbations in the waveguide. This approach is based on the first order Born approximation and takes into account the finite-frequency effects associated with wave propagation. The robustness the TASK approach is analyzed and compared to numerical parabolic equation simulations involving different sound speed perturbations. For example, parameters such as the perturbation location, the value and shape of the perturbation in the waveguide are modified. The combination of several perturbations and the influence of the source-receiver array apertures on the TT, DOA and DOD estimates are also studied.

  • Open Access English
    Authors: 
    Ye, Y.; Wagener, T.; Völker, C.; Guieu, C.; Wolf-Gladrow, D. A.;
    Project: EC | DAPOP (236694), ANR | DUNE (ANR-07-BLAN-0126)

    A significant decrease of dissolved iron (DFe) concentration has been observed after dust addition into mesocosms during the DUst experiment in a low Nutrient low chlorophyll Ecosystem (DUNE), carried out in the summer of 2008. Due to low biological productivity at the experiment site, biological consumption of iron can not explain the magnitude of DFe decrease. To understand processes regulating the observed DFe variation, we simulated the experiment using a one-dimensional model of the Fe biogeochemical cycle, coupled with a simple ecosystem model. Different size classes of particles and particle aggregation are taken into account to describe the particle dynamics. DFe concentration is regulated in the model by dissolution from dust particles and adsorption onto particle surfaces, biological uptake, and photochemical mobilisation of particulate iron. The model reproduces the observed DFe decrease after dust addition well. This is essentially explained by particle adsorption and particle aggregation that produces a high export within the first 24 h. The estimated particle adsorption rates range between the measured adsorption rates of soluble iron and those of colloidal iron, indicating both processes controlling the DFe removal during the experiment. A dissolution timescale of 3 days is used in the model, instead of an instantaneous dissolution, underlining the importance of dissolution kinetics on the short-term impact of dust deposition on seawater DFe. Sensitivity studies reveal that initial DFe concentration before dust addition was crucial for the net impact of dust addition on DFe during the DUNE experiment. Based on the balance between abiotic sinks and sources of DFe, a critical DFe concentration has been defined, above which dust deposition acts as a net sink of DFe, rather than a source. Taking into account the role of excess iron binding ligands and biotic processes, the critical DFe concentration might be applied to explain the short-term variability of DFe after natural dust deposition in various different ocean regions.

  • Open Access English
    Authors: 
    Burckel, Pierre; Waelbroeck, Claire; Luo, Yiming; Roche, Didier M; Pichat, Sylvain; Jaccard, Samuel L; Gherardi, Jeanne-Marie; Govin, Aline; Lippold, Jörg; Thil, François;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | ACCLIMATE (339108), SNSF | SeaO2 - Past changes in S... (144811), ANR | RETRO (ANR-09-BLAN-0347), SNSF | Quantifying changes in th... (111588)

    We reconstruct the geometry and strength of the Atlantic Meridional Overturning Circulation during Heinrich Stadial 2 and three Greenland interstadials of the 20-50 ka period based on the comparison of new and published sedimentary 231Pa/230Th data with simulated sedimentary 231Pa/230Th. We show that the deep Atlantic circulation during these interstadials was very different from that of the Holocene. Northern-sourced waters likely circulated above 2500 m depth, with a flow rate lower than that of the present day North Atlantic Deep Water (NADW). Southern-sourced deep waters most probably flowed northwards below 4000 m depth into the North Atlantic basin, and then southwards as a return flow between 2500 and 4000 m depth. The flow rate of this southern-sourced deep water was likely larger than that of the modern Antarctic Bottom Water (AABW). Our results further show that during Heinrich Stadial 2, the deep Atlantic was probably directly affected by a southern-sourced water mass below 2500 m depth, while a slow southward flowing water mass originating from the North Atlantic likely influenced depths between 1500 and 2500 m down to the equator.

  • Other research product . Other ORP type . 2015
    Open Access
    Authors: 
    de Vargas, Colomban; Probert, Ian; Carmichael, Margaux; Poulain, Julie; Romac, Sarah; Colin, Sébastien; Aury, Jean-Marc; Bittner, Lucie; Chaffron, Samuel; Dunthorn, Micah; +45 more
    Project: TARA | Tara Oceans (2)

    Accompanying material, text, data and figures for the article de Vargas et al., 'Eukaryotic plankton diversity in the sunlit ocean', Science 348, 1261605 (2015), doi: 10.1126/science.1261605

  • Open Access English
    Authors: 
    Sourdeval, Odran; Gryspeerdt, Edward; Krämer, Martina; Goren, Tom; Delanoë, Julien; Afchine, Armin; Hemmer, Friederike; Quaas, Johannes;
    Project: EC | QUAERERE (306284), EC | MSCCC (703880)

    The number concentration of cloud particles is a key quantity for understanding aerosol–cloud interactions and describing clouds in climate and numerical weather prediction models. In contrast with recent advances for liquid clouds, few observational constraints exist regarding the ice crystal number concentration (Ni). This study investigates how combined lidar–radar measurements can be used to provide satellite estimates of Ni, using a methodology that constrains moments of a parameterized particle size distribution (PSD). The operational liDAR–raDAR (DARDAR) product serves as an existing base for this method, which focuses on ice clouds with temperatures Tc<-30 ∘C. Theoretical considerations demonstrate the capability for accurate retrievals of Ni, apart from a possible bias in the concentration in small crystals when Tc≳−50 ∘C, due to the assumption of a monomodal PSD shape in the current method. This is verified via a comparison of satellite estimates to coincident in situ measurements, which additionally demonstrates the sufficient sensitivity of lidar–radar observations to Ni. Following these results, satellite estimates of Ni are evaluated in the context of a case study and a preliminary climatological analysis based on 10 years of global data. Despite a lack of other large-scale references, this evaluation shows a reasonable physical consistency in Ni spatial distribution patterns. Notably, increases in Ni are found towards cold temperatures and, more significantly, in the presence of strong updrafts, such as those related to convective or orographic uplifts. Further evaluation and improvement of this method are necessary, although these results already constitute a first encouraging step towards large-scale observational constraints for Ni. Part 2 of this series uses this new dataset to examine the controls on Ni.

  • English
    Authors: 
    Lucken, Michael;
    Publisher: HAL CCSD
    Country: France

    Michael Lucken est un historien et historien de l’art français. Enseignant à l’Inalco depuis 1998, il est nommé en 2010 membre de l’Institut Universitaire de France. Il réalise à compter de cette date plusieurs missions en Asie de l’Est et dans le Pacifique dans le but de documenter les monuments et lieux de mémoire de la Seconde Guerre mondiale dans cette région du monde. Il est l’auteur, entre autres, de 1945-Hiroshima : les images-sources (Hermann, 2008) et Les Japonais et la guerre, 1937-1952 (Fayard, 2013).; Débris d'un bombardier japonais, en service de 1940 à 1945.