Application of modern analog technique to marine Antarctic diatoms: Reconstruction of maximum sea-ice extent at the Last Glacial Maximum
Modern analog technique (MAT) applied to Antarctic diatoms is a new approach for quantitative sea‐ice paleoreconstructions in the Southern Ocean. In a first step we show that MAT is a better approach than the Imbrie and Kipp Method to reconstruct the modern sea‐ice pattern. We then use this approach to reconstruct sea‐ice presence in number of months per year during the last glacial maximum (LGM). At this time, sea‐ice presence was greater than today, leading to a shorter diatom growing season. The maximum sea‐ice extent, inferred from quantitative values of sea‐ice presence, was located 5–8° north of its actual position, leading to double the surface of modern winter sea ice. This greater sea‐ice extent may have played a significant role on atmospheric and surface oceanic circulations and therefore on southern mid‐latitude and high‐latitude climates. It may also have reduced the amount of heat, moisture, and CO2 from the ocean to the atmosphere, thus participating in the lowering of atmospheric CO2 during the LGM
(Paleoceanography. vol. 13, n° 0883-8305, pp. 284-297, 23/05/1998)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LDEO
Acceleration of Horizontal Mean Currents in DNS of Stratified Turbulent Shear Flows
(. vol. 46, pp. 423-424, 23/05/1998)
IMFT, UT3, Comue de Toulouse, CNRS, Toulouse INP, Comue de Toulouse, CERFACS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Compositions isotopiques (Sr, Pb, Nd) et analyses des terres rares de sédiments métallifères de la Mer Rouge
(23/05/1998)
LHyGeS, ENGEES, UNISTRA, INSU - CNRS, CNRS, UAG, INSU - CNRS, UM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Migration of micropollutants in a dredging amended soil in Northern France
A river dredging sludge containing heavy metals and organic compounds was spread on an unsaturated soil in Northern France, and the evolution of the micro-pollutants was studied for 28 months. Metal concentration were higher after 28 months, whereas there was no accumulation of organic compounds. The metal balance in the soil was good, which was not the case for organic carbon. The unbalance could be explained by an increased mineralization of both the initial and the xenobiotic organic matter, induced by the addition of easily-biodegradable organic carbon into the soil and by humification. Micro-pollutant concentrations in the top layer of soil remained very high which could induce a contamination of plants.
(Agrochimica. vol. 42, pp. 69--71, 23/05/1998)
IFSTTAR/GERS/EE, IFSTTAR, UNAM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SRSN [Poitiers], UP, INC-CNRS, CNRS
The last Glacial Period: rapid changes in air temperature and ocean hydrology
(PAGES News. vol. 5, n° 1811-1602, pp. 15-16, 01/08/1997)
CFR, CEA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Potential of bivalves' secondary settlement differs with species: a comparison between cockle ( Cerastoderma edule ) and clam ( Ruditapes philippinarum ) juvenile resuspension
Juvenile bivalves may be dispersed by entering a bysso-pelagic phase where they drift through the water mass aided by a long thread. The ability to resuspend and control the specific weight in two bivalve species, the cockle Cerastoderma edule (L.) and the Japanese clam Ruditapes philippinarum (Adams and Reeves), was documented with juveniles through flume and still-water experiments. Cockle juveniles initially placed on an unsuitable substratum were exposed to two shear velocities (u *). At the end of the experiment, 42 (±15)% (for u *=0.51 cm s−1) and 79 (±9)% (for u *=0.99 cm s−1) of individuals were retrieved from the sand area which represents only 8% of the total flume surface. Most juveniles (70.5%) with shell lengths <2.5 mm migrated from the unsuitable Plexiglas substratum to the sand array by resuspension in the water column. The percentage was lower (21.5%) for larger individuals. The same experimental design was applied to clams, which immediately adhered to the Plexiglas substratum and remained attach to it. Sinking rates of live and dead specimens of both species were measured in a 1 m long transparent PVC tube. Cockle fall velocities showed severe deceleration, probably due to byssus secretion (up to 15-fold slower than dead cockles), sometimes interrupted by brutal acceleration probably due to byssal rupture. Cockles were able to reduce their sinking rate for shell lengths up to 4.25 mm. By contrast, clam sinking rates were constant, and similar to dead clam sinking rates. Specific weights of all experimental juveniles were calculated in relation to their lengths, and their passive motion into the boundary layer was theoretically assessed with Shields curve. In short, C. edule and R. philippinarum can both exhibit dense populations in the field with a good capacity to colonize, although juveniles display different abilities to resuspend in the water column.
(Marine Biology. vol. 128, n° 0025-3162, pp. 639-648, 31/05/1997)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Distribution of Chaetoceros resting spores in modern peri-Antarctic sediemnts
(Marine Micropaleontology, n° 0377-8398, 15/02/1997)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Delphes - Reconstitution Tridimensionnelle du Sanctuaire d'Athéna
a reconstitution virtuelle tridimensionnelle du sanctuaire d'Athéna à Delphes a été réalisée dans le cadre d'une action de Mécenat Technologique et Scientifique d'EDF par l'Ecole d'Architecture de Nancy, la Maison de l'Archéologie de Bordeaux et la Direction des Etudes et Recherches d'EDF, au profit de l'Ecole Française d'Athènes. Cette collaboration entre architectes, informaticiens et archéologues constitue une première dans ce domaine, dans la mesure où il ne s'agissait pas uniquement de restituer et de visualiser des monuments disparus, mais aussi d'utiliser les outils de modélisation pour faire avancer les connaissances relatives à l'architecture du site. D'un côté, la part d'incertitude concernant l'architecture et l'aspect de la célèbre Tholos de Delphes, par exemple, a ainsi été fortement réduite. De l'autre, la reconstitution en 3D qui intégre les couleurs antiques et l'aspect des matériaux, a été replacée dans son environnement physique. Ces résultats ont pu être obtenus grâce à deux dispositifs. D'une part, une campagne de relevé sur place au moyen du scanner tridimensionnel SOISIC a permis de vérifier et de compléter les informations issues des précédentes études des vestiges. D'autre part, les bases de données ont été organisées pour définir plusieurs maquettes des bâtiments (maquettes d'étude très détaillées, allant jusqu'au niveau des blocs, maquettes avec décoration, maquettes d'évolution, intégrant les différentes phases de transformations du sanctuaire, sur une période de huit siècles). Les résultats sont présentés dans deux ouvrages à paraître et sous forme d'un film retraçant les différentes étapes du travail sur le site et dans les laboratoires. De plus, une promenade en relief dans l'espace virtuel reconstitué dessine le nouveau visage de l'ensemble des édifices qui composent le sanctuaire d'Athéna.
(01/02/1997)
MAP, INSA Strasbourg, INSA, MCC, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Evidence for changes in the North Atlantic Deep Water linked to meltwater surges during the Heinrich events
(Earth and Planetary Science Letters. vol. 146, n° 0012-821X, pp. 13-27, 01/01/1997)
CFR, CEA, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Along-axis dynamic topography constrained by major-element chemistry
Variations in thickness and density of both the crust and the associated upper mantle have been derived from a compilation of zero-age major-element composition along the Mid-Atlantic Ridge, the East Pacific Rise and the Southeast Indian Ridge. Assuming isostatic compensation, the axial depth computed from major-element data correctly agrees with observed axial depth. Discrepancies are essentially located near hotspots such as Iceland and Azores. The residual topography, expressed as the difference between observed and compensated axial depth has a root-mean-square of 426 m along the three spreading axes, which is below the resolution power of the method. This insignificant topography, which is assumed to contain the dynamic surface topography associated with mantle convection, bears an important constraint on the relative variations of the dynamic topography predicted by models of mantle circulation.
(Earth and Planetary Science Letters. vol. 149, n° 0012-821X, pp. 49-56, 23/05/1997)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, LST, ENS de Lyon, UCBL, INSU - CNRS, CNRS