New constraints on European glacial freshwater releases to the North Atlantic Ocean
During the late Quaternary, both external and internal forcings have driven major climatic shifts from glacial to interglacial conditions. Nonlinear climatic steps characterized the transitions leading to these extrema, with intermediate excursions particularly well expressed in the dynamics of the Northern Hemisphere cryosphere. Here we document the impact of these dynamics on the north-eastern North Atlantic Ocean, focussing on the 35-10 ka interval. Sea-surface salinities have been reconstructed quantitatively based on two independent methods from core MD95-2002, recovered from the northern Bay of Biscay adjacent to the axis of the Manche paleoriver outlet and thus in connection with proximal European ice sheets and glaciers. Quantitative reconstructions deriving from dinocyst and planktonic foraminiferal analyses have been combined within a robust chronology to assess the amplitude and timing of hydrological changes in this region. Our study evidences strong pulsed freshwater discharges which may have impacted the North Atlantic Meridional Overturning Circulation.
(Geophysical Research Letters. vol. 39, n° 0094-8276, pp. L15601, 01/08/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, GEOTOP, EPM, UdeM, UQAT, UQAR, UQAM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, LDO, INSU - CNRS, UBO EPE, CNRS, GM, IFREMER
Global characterization of the Holocene Thermal Maximum
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: a b s t r a c t We analyze the global variations in the timing and magnitude of the Holocene Thermal Maximum (HTM) and their dependence on various forcings in transient simulations covering the last 9000 years (9 ka), performed with a global atmosphere-ocean-vegetation model. In these experiments, we consider the influence of variations in orbital parameters and atmospheric greenhouse gases and the early-Holocene deglaciation of the Laurentide Ice sheet (LIS). Considering the LIS deglaciation, we quantify separately the impacts of the background melt-water fluxes and the changes in topography and surface albedo. In the analysis we focus on the intensity of the maximum temperature deviation relative to the preindustrial level, its timing in the Holocene, and the seasonal expression. In the model, the warmest HTM conditions are found at high latitudes in both hemispheres, reaching 5 C above the preindustrial level, while the smallest HTM signal is seen over tropical oceans (less than 0.5 C). This latitudinal contrast is mostly related to the nature of the orbitally-forced insolation forcing, which is also largest at high latitudes, and further enhanced by the polar amplification. The Holocene timing of the HTM is earliest (before 8 ka BP) in regions not affected by the remnant LIS, particularly NW North America, E Asia, N Africa, N South America, the Middle East, NE Siberia and Australia. Compared to the early Holocene insolation maximum, the HTM was delayed by 2e3 ka over NE North America, and regions directly downwind from the LIS. A similar delay is simulated over the Southern Ocean, while an intermediate lag of about 1 ka is found over most other continents and oceans. The seasonal timing of the HTM over continents generally occurs in the same month as the maximum insolation anomaly, whereas over oceans the HTM is delayed by 2e3 months. Exceptions are the oceans covered by sea ice and North Africa, were additional feedbacks results in a different seasonal timing. The simulated timing and magnitude of the HTM are generally consistent with global proxy evidence, with some notable exceptions in the Mediterranean region, SW North America and eastern Eurasia.
(Quaternary Science Reviews. vol. 48, n° 0277-3791, pp. 7-19, 01/08/2012)
UvA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, TECLIM, ELI, UCLouvain, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA
THE END OF A MYTH: ARPYLORUS ANTIQUUS PALEOZOIC DINOFLAGELLATE CYST
Arpylorus antiquus, erected by Calandra in 1964, was isolated from upper Silurian sedimentary rocks from the Mechiguig 1 borehole in southern Tunisia, with other palynomorphs. The folded vesicle and the quadrangular form of the aperture break down into platelike fragments, resembling the tabulation of dinoflagellates. The presence of these elements has been used to interpret A. antiquus as a dinoflagellate cyst. The morphology and affinity of A. antiquus is reinterpreted herein based on investigation of larger sets of samples, including material from the type locality, together with material of Algeria, Saudi Arabia, and Brazil. More complete specimens than those previously described have been observed using gentle laboratory techniques, showing a large development of a fine membrane at the periphery of vesicles. This element was destroyed using classical palynological treatments, implying that the holotype is an incomplete specimen. The membrane at the periphery of vesicles and dorsoventral differentiation of these vesicles suggest that A. antiquus is a part of a more complex biological structure. We suggest a possible relationship with eurypterids, arthropods related to phyllocarids, represented by abundant fragments in the assemblages. Arpylorus antiquus is possibly a structure of storage. The chemical composition of A. antiquus using a Fourier transform infrared FTIR microspectroscopy analysis, reveals a wall composed of biopolymer that is not consistent with dinosporin. We conclude that Arpylorus antiquus is definitively not a dinoflagellate cyst. Although dinoflagellates may have older Paleozoic or even Proterozoic ancestors as the biomarker record may suggest, the dinoflagellate tabulation evolved only in the early Mesozoic.
(Palaios. vol. 27, n° 0883-0351, pp. 414-423, 26/07/2012)
LDO, INSU - CNRS, UBO EPE, CNRS, CR2P, MNHN, UPMC, CNRS, ULiège, KU
Changements globaux, inondations et terres viticoles : une combinaison à risque pour la qualité des eaux de l’estuaire de la Gironde ?
La fréquence et l’intensité des événements extrêmes, associés à l’élévation du niveau de la mer, prendraient une ampleur sans précédent en raison du changement climatique. Le cumul de ces deux phénomènes provoquerait une augmentation des inondations par crues et submersions marines, notamment sur les zones estuariennes aux interfaces complexes entre terre, mer et fleuve. Le Médoc, sur la rive gauche de l’estuaire de la Gironde, occupé historiquement par des terres viticoles, a subi de graves inondations lors d’événements récents (tempêtes Martin en 1999 et Xynthia en 2010). La remise en eau temporaire de ces terres, fortement contaminées en certains métaux, pourrait avoir des impacts géochimiques sur la qualité des sols et des eaux de l’estuaire. Dans une démarche pluridisciplinaire, associant géochimie, géographie et géomatique, nous proposons d’étudier ces impacts à partir d’une double approche. Après avoir caractérisé les événements météorologiques affectant le Médoc, nous avons déterminé des communes viticoles sensibles aux risques d’inondation à partir de base de données publiques : BD Gaspar sur les arrêtés de catastrophes naturels, BD Agreste pour les surfaces en vigne et BD Primnet pour les zones couvertes par des plans de prévention des risques inondation (approche spatio-statistique). Dans ces communes, nous avons collecté des sols qui ont subi des tests de lixiviation en laboratoire ; les sols ont été mis en contact avec l’eau douce ou estuarienne, afin d’identifier les processus de relargages ou piégeages en métaux et simuler ainsi l’impact des inondations (approche expérimentale). Cette étude s’inscrit dans un programme de recherche pluridisciplinaire Adapt’eau (ANR CEP&S 2011) qui vise à étudier les impacts des changements globaux et à expérimenter des options d’adaptation, notamment la dépoldérisation.
(pp. 1, 09/07/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR ADBX, IRSTEA
Stratégie bio-analytique de type EDA pour l’identification de contaminants émergents dans les milieux aquatiques : Etude de cas en aval d’un rejet industriel
(04/07/2012)
INERIS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, CNRS
Application de modèles non paramétriques sous R pour l'analyse et le suivi de la qualité de l'eau
Application de modèles non paramétriques sous R pour l'analyse et le suivi de la qualité de l'eau
(02/07/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Les cartes auto-organisatrices de Kohonen appliquées à l'étude des communautés de micro-algues des cours d'eau
Les cartes auto-organisatrices de Kohonen appliquées à l'étude des communautés de micro-algues des cours d'eau
(02/07/2012)
UR REBX, IRSTEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, INRS - ETE, INRS, PACEA, UB, CNRS
Application de modèles non paramétriques sous R pour l'analyse et le suivi de la qualité de l'eau
Application de modèles non paramétriques sous R pour l'analyse et le suivi de la qualité de l'eau
(02/07/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
On the use of linear stability model to characterize the morphological behaviour of a double bar system. Application to Truc Vert Beach (France).
Sandy barred beaches are often characterized by the presence of rhythmic patterns such as crescentic bars. In this paper, a linear stability analysis (LSA) model is used to characterize the morphological behaviour of the double bar system of Truc Vert beach. Using a limited number of combination of representative bathymetries, wave classes and water levels, the morphodynamic response of the system is analysed, focussing on the geometrical characteristics of 3D patterns generated with the model. These characteristics are described and then compared with available observations. The shapes and the wavelengths of the instabilities predicted by the model compare well with field observations. Thus, the use of linear stability model, with representative hydrodynamic conditions and bathymetries of the considered site, allows a characterization of the global morphodynamic behaviour of a double-barred system.
(Comptes Rendus. Géoscience. vol. 344, n° 1631-0713, pp. 277-287, 28/06/2012)
BRGM, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UPC, UPC
Are antioxidant and transcriptional responses useful for discriminating between chemo- and radiotoxicity of uranium in the crayfish Procambarus clarkii?
The main objectives of this study were to evaluate uranium (U) toxicity in the crayfish Procambarus clarkii at a low dose of exposure and to discriminate between the chemotoxicity and radiotoxicity of U. We conducted two sets of experiments using either 30μgL -1 of depleted uranium (DU) or 233U, which differ from each other only in their specific activity (DU=1.7×10 4Bqg -1, 233U=3.57×10 8Bqg -1). The endpoints were oxidative stress responses and mitochondrial functioning in the gills and hepatopancreas, which were measured in terms of enzyme activities and gene expression levels. U accumulation levels were measured in different organs (gills, hepatopancreas, stomach, intestine, green gland, muscles, and carapace), and internal dose rates in the hepatopancreas were compared after DU and 233U exposures. Significant U accumulation occurred in the organs of P. clarkii, and mitochondrial damage and antioxidant responses were detected. Despite the huge difference (21,000×) in the specific activities of DU and 233U, few significant differences in biological responses were detected in P. clarkii exposed to these two pollutants. This finding indicates that the radiotoxicity was low compared to the chemotoxicity under our exposure conditions. Finally, genes expression levels were more sensitive markers of U toxicity than enzyme activities. © 2012 Elsevier Inc.
(Ecotoxicology and Environmental Safety. vol. 80, n° 0147-6513, pp. 266-272, 01/06/2012)
IRSN/DEI/SECRE/LRE, IRSN/DEI/SECRE, IRSN, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UNIPG, IRSN/DEI/SECRE/LME, IRSN/DEI/SECRE, IRSN